JPH11190614A - Wall thickness measuring device for glass vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wall thickness measuring device that can measure the wall thickness of a glass vessel stably and accurately using laser beams. SOLUTION: A wall thickness measuring device for a glass vessel is provided with a laser beam source 1 for making laser beams enter the glass vessel 3, a photographing means 5 for photographing the beam trace K of laser beams from the outer surface A of the glass vessel 3 to the inner surface B, a filter 7 excluding beams with wavelength other than the wavelength of beams showing the beam trace K, from incident beams to the photographing means 5, and a computing means 11 for computing the wall thickness of the glass vessel 3 from an image photographed by the photographing means 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass container thickness measuring apparatus for optically measuring, for example, a body thickness of a glass container by using a laser beam.

[0002]

2. Description of the Related Art Conventionally, there has been known a measuring device for optically measuring the thickness of a body of a glass container using a laser beam (for example, Japanese Patent Application Laid-Open No. Hei 6-201336).

[0003] The measuring device described in this publication irradiates a laser beam into a glass container and shoots a distance between a light spot on the outer surface of the glass container and a light spot on the inner surface with an image pickup device. The method of calculating the thickness of the glass container from this image is adopted.

[0004]

However, according to the above-mentioned technology, the cleaner the inner surface of the glass container, the more difficult it is to cause irregular reflection of light. Therefore, it is difficult to find a light spot on the inner surface. If dust adheres to the surface, the shape of the light spot on the outer surface will be deformed, making it difficult to find the light spot on the outer surface.Furthermore, light spots due to virtual images will be generated, making image processing difficult. There is a problem that an error is caused in the thickness measurement.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to measure the thickness of a glass container stably and accurately using a laser beam. It is to provide a device.

[0006]

According to the first aspect of the present invention,
A laser light source for injecting a laser beam into a glass container, a photographing means for photographing a light trace of excitation light from the outer surface to the inner surface of the glass container caused by the laser light from the laser light source, A filter that excludes light having a wavelength other than the wavelength of the excitation light from the incident light; and a calculating unit that calculates the thickness of the glass container based on the light trace captured by the capturing unit. It is characterized by the following.

According to a second aspect of the present invention, in the first aspect, the laser light source is angled so that the incident angle of the laser beam on the inner surface of the glass container does not exceed a critical angle which is a condition of total reflection. It is characterized by having been installed with.

According to a third aspect of the present invention, in the first or second aspect, the photographing means is installed at an angle so as not to receive the regular reflection of the laser light on the outer surface of the glass container. It is characterized by the following.

According to a fourth aspect of the present invention, in the first aspect, the laser light source comprises a semiconductor laser, and the semiconductor laser is provided with a convergent lens comprising an achromatic lens. It is characterized by the following.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the calculating means corrects the measurement difference caused by the curvature of the glass container by geometrical optics. It is characterized by comprising means.

[0011]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

(1) Overall Configuration In FIGS. 1 and 2, reference numeral 1 denotes a laser light source. The laser beam from the laser light source 1 reaches the outer surface A of the body 3 a of the glass container 3 after being converged by the converging lens 2. After reaching the outer surface A, the light is refracted by the outer surface A, travels straight through the body 3a of the glass container 3, reaches the inner surface B, and is refracted by the inner surface B. Enter the interior space. The light trace K of the light traveling straight between the outer surface A and the inner surface B of the glass container 3 is photographed by a CCD camera (“photographing means”) 5. Laser light source 1 and CCD camera 5
Are arranged in the same plane as shown in FIG.

The light trace K of light captured by the CCD camera 5 is excitation light generated by the absorption of laser light by impurity ions (such as transition metal ions or rare earth ions) in glass. The light has a wavelength longer than the wavelength of the laser light output from the laser light source 1.

Therefore, only the excitation light is supplied to the CCD camera 5.
The CCD camera 5 and the glass container 1
And a filter 7 for excluding all light (for example, laser light) having a wavelength other than the wavelength of the light that represents the light trail K.
Is arranged.

The light trace K of the light captured by the CCD camera 5 is input to the computer 11, where it is subjected to image processing, and the thickness of the glass container 3 is calculated from the length of the light trace K. More specifically, the number of pixels formed by the light trace K is measured, and the thickness is calculated from the number of pixels.

Although not shown, the glass container 3 is placed on a rotating disk. According to this, the glass container 3
By continuously detecting the light trace K while rotating, the thickness of the entire circumference of the glass container 3 is automatically measured.

(2) Improvement of Light Trace Luminance a) Light Emission Side Since the luminance of the excitation light from the light trace K is low, it is necessary to improve the luminance. In order to improve the brightness of this excitation light, while increasing the optical power per unit volume,
It is necessary to select a laser light source in a wavelength region where the light absorption of ions in the glass is large. The brightness of the light trace K changes according to the wavelength of the incident laser light.

The degree of absorption of the wavelength of the incident light by the impurity ions (such as transition metal ions or rare earth ions) in the glass is determined. In general, the absorption of the wavelength of the incident light becomes large in the visible light region.

In this embodiment, a semiconductor laser having a wavelength of 685 nm and an optical power of 30 mW, for example, is used as the laser light source 1 as a laser having a wavelength in the visible light region and a large optical power. According to this, a light intensity of 20 mW is obtained on the outer surface A.

B) Improvement of Light Density In order to improve the light density by converging the laser light from the laser light source 1 while suppressing the occurrence of aberration, the convergent lens 2 is provided with an achromatic lens dedicated to a semiconductor laser. Etc. are used.

C) Light receiving side In order to efficiently detect the light trace (excitation light) K on the CCD camera 5 side, it is necessary to reliably detect only the wavelength component without reducing the wavelength component emitted by the excitation light. Required. For this purpose, a filter 7 is arranged between the CCD camera 5 and the glass container 3. The filter 7 is selected to remove almost 100% of the wavelength (685 nm) of the laser light from the laser light source 1 and to transmit almost 100% of the wavelength longer than 685 nm.

In addition, the CCD camera 5 has 685 nm
A camera having high sensitivity in a region of light (near infrared light) having a longer wavelength than that of the camera is selected.

D) Laser Injection In order to improve the incidence rate on the outer surface A of the glass container 3 and to suppress total reflection on the inner surface B, laser light from the laser light source 1 is P-polarized. By the way, when the laser beam is incident on P-polarized light, when the refractive index of the glass is set to 1.5, the glass becomes totally transmitted when the incident angle θb called the Brewster angle is θb = 56.3 ° from the air to the glass, and the glass transmits the air. The incident angle θb called the Brewster angle is θb
= 33.7 °, total transmission. With this P-polarized light incidence, the reflectance can be suppressed lower at an angle close to the Brewster's angle than with S-polarized light incidence.

When total reflection occurs on the inner surface B, a light trace (excitation light) K 'is generated.
When it is incident on the, it becomes disturbance light.

In order not to cause total reflection on the inner surface B of the glass container 3, in the case of the glass container 3 having a large thickness variation and a small diameter, the incident angle on the inner surface B is the critical angle (the total reflection condition). The installation angle of the laser light source 1 is set so as not to be equal to or more than the critical angle when the refractive index of the glass is 1.5 (41.8 °).

(3) Shape of incident beam Laser light having a wavelength of 685 nm is emitted from the laser light source 1 as parallel light, and this parallel light is converged by a convergent lens 2 composed of an achromatic lens so as to reduce aberration. It is desirable to use a lens having a focal depth close to the thickness of the glass container 3 to be measured as the converging lens 3.

The focal length of the converging lens 3 is 100 mm
It is. The beam shape from the laser light source 1 has a major axis of 4 mm,
It is an elliptical shape with a short axis of 2 mm. Depth of focus I in the long axis direction
Is I = ± λ / 2NA2. Where NA = sin
θ, tan θ = 2/100 = 0.02, λ = 685 nm
Therefore, I = ± 0.856 nm.

This depth of focus I corresponds to about 2 mm,
Even a glass container 3 having a thickness of 5 mm can be sufficiently squeezed for observation. The diameter of the portion most narrowed down by the beam shape of the laser beam is d = 20.9 from d = 0.61λ / NA.
μm.

(4) Preferred Installation Angle of Laser Light Source and CCD Camera a) Problems Regarding Installation Angle For example, the incident angle of the laser beam output from the laser light source 1 is set to 0 °, and the installation angle of the CCD camera 5 ( When the angle between the normal and the normal is set to 40 °, the computer 1
For example, as shown in FIG. 3, an elongated virtual image 9 is observed following the light trace K on the display unit 11a.

The wavelength of the virtual image 9 coincides with the wavelength of the light trace K, becomes disturbance light, and the luminance sometimes becomes high. Therefore, when the virtual image 9 is observed following the light trace K, the virtual image 9 becomes glass. This causes an error in measuring the thickness of the container 3. Therefore,
As shown in FIG. 2, it is desirable to determine the installation angles of the laser light source 1 and the CCD camera 5 so that the virtual image 9 is hidden behind the light trace K when viewed from the CCD camera 5.

For example, the incident angle of the laser beam output from the laser light source 1 is set to 45 °, and the diameter is 34 mm.
When the thickness measurement of the glass container 3 is performed, total reflection occurs at a portion where the thickness of the inner surface B of the glass container 3 changes drastically, and a light trace K ′ resulting from the total reflection is observed.

The wavelength of the light trace K 'coincides with the wavelength of the light trace K, becomes disturbance light, and the luminance sometimes becomes high. Therefore, when the light trace K' is observed following the light trace K, Light trail K '
Causes an error in measuring the thickness of the glass container 3.

However, since the light trace K 'is generated only in a part of the entire periphery of the glass container 3, it is possible to eliminate the light trace K' from the measured data by differentiating the measured thickness data. it can. However, when the incident angle of the laser light is set to 45 ° or more, the frequency of occurrence of the light trace K ′ increases.
Setting above is not preferable.

It is not preferable that the regular reflection light K ″ of the laser light on the outer surface A is directly incident on the CCD camera 5 because disturbance light is generated.

The regular reflection light K ″ of the laser beam has a wavelength different from the wavelength of the light trace K. Therefore, the regular reflection light K ″ is normally removed by the filter 7, but the power of the laser light source 1 This is because if the intensity of the light is increased, the specularly reflected light K ″ may pass through the filter 7 and directly enter the CCD camera 5.

When the incident angle of the laser light output from the laser light source 1 is set to an acute angle, the light trace K becomes perpendicularly incident, and the depth of focus of the light trace K becomes deeper when viewed from the CCD camera 5. Is unfavorable because "blurring" occurs.

B) Installation Angle In order to improve the measurement accuracy, when the appearance of the virtual image 9 is considered, the laser incident angle 0 to 20 ° becomes a problem area, and the appearance of the light trace K ′ due to total reflection is reduced. In consideration of this, in the glass container 3 having a small diameter, a laser incident angle of 45 ° or more becomes a problem section, and therefore it is desirable to avoid this section. In consideration of the above, the most preferable installation angle for preventing the light trace K from being “blurred” and preventing the laser light from being incident on the CCD camera 5 is as follows: the laser incident angle is 40 to 45 °, and the installation angle of the CCD camera 5 ( Angle with respect to the normal) is 15 to 25 °.

(5) Optical Correction As the thickness of the glass container 3 having a small diameter increases, a difference occurs between the actual thickness value and the measured value as shown in FIG. Since this difference is affected by the curvature of the glass container 3, it can be corrected geometrically. In the case of geometrical optical correction, the refractive index of the glass container 3, the laser incident angle, the installation angle of the CCD camera 5, the diameter of the glass container 3, and the length of the light trace K are substituted into a predetermined calculation formula. Is done. According to this correction, as shown in FIG. 5, the actual thickness value substantially matches the measured value.

The calculation is performed by a computer 11, which constitutes a calculating means for calculating the thickness of the glass container 3 and a correcting means for correcting a deviation of the measured value of the glass container 3 due to the curvature. I do.

(6) Conclusion a) In this embodiment, only the wavelength of the light trace K is incident on the CCD camera 5 very efficiently to measure the thickness of the glass container 3, so that flint (transparent), amber, dark It is possible to measure the thickness of the glass container 3 of most colors such as smoke and emerald green.

However, since the brightness of the light trace K slightly changes due to the difference in color of the glass container 3, it is necessary to adjust the sensitivity of the CCD camera 5 and the like.

B) Even when the diameter of the glass container 3 is different, it is possible to measure the wall thickness almost accurately by correcting the curvature using a predetermined calculation formula.

C) Measurement can be sufficiently performed up to a thickness of 5 mm of the glass container 3.

D) Since the light trace K is detected through the filter 7, the light trace K is hardly affected by disturbance light.

E) In this embodiment, high precision, non-contact,
The thickness of the glass container 3 can be measured with high stability, easily, and at high speed. According to this, the number of measuring points is increased, the reliability of the measured value is improved, and the frequency of the periodic measurement is increased. Therefore, the thickness information fed back from the measuring device is more substantial than the conventional one. Therefore, thickness control and control of the glass container 3 can be easily performed.

Although the present invention has been described based on one embodiment, the present invention is not limited to this. For example, the measurement of the thickness of the glass container 3 has been described, but the present invention is also applicable to the measurement of the thickness of a glass plate.

[0047]

According to these inventions, the thickness of a glass container can be measured with extremely high precision using a laser beam.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram also shown in a horizontal section.

FIG. 3 is a plan view showing a virtual image.

FIG. 4 is a diagram showing a measurement result before correction.

FIG. 5 is a diagram showing a measurement result after correction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser light source 2 Convergent lens 3 Glass container 5 CCD camera (photographing means) 7 Filter 9 Virtual image 11 Computer (calculation means, correction means) A Outer surface B Inner surface

Claims (5)

[Claims] 1. A laser light source for injecting a laser beam into a glass container, and a photographing means for photographing a light trace of excitation light from the outer surface to the inner surface of the glass container caused by the laser light from the laser light source. A filter that excludes light having a wavelength other than the wavelength of the excitation light from the light incident on the photographing unit, and a calculating unit that calculates the thickness of the glass container based on the light trace photographed by the photographing unit. And a thickness measuring device for a glass container. 2. The laser light source according to claim 1, wherein an angle of incidence of the laser light on the inner surface of the glass container is set so as not to exceed a critical angle which is a condition of total reflection. Thickness measuring device for glass containers. 3. The meat of a glass container according to claim 1, wherein said photographing means is installed at an angle so as not to receive regular reflection of laser light on the outer surface of said glass container. Thickness measuring device. 4. The glass container according to claim 1, wherein said laser light source is a semiconductor laser, and said semiconductor laser is provided with a convergent lens comprising an achromatic lens. Thickness measuring device. 5. The glass according to claim 1, wherein the calculation unit includes a correction unit that geometrically corrects a measurement difference caused by the curvature of the glass container. Container thickness measuring device.