JPS5860244A - Method of inspecting transparent material strip - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a transparent material strip, particularly a flat glass.
Scanning the strip of material with a moving light spot across the width of the strip and receiving transmitted and/or reflected light to inspect for defects such as foreign objects or air bubbles contained in the strip. The present invention relates to a method for inspecting a transparent material strip, which comprises converting it into an electrical signal and evaluating it.

Transparent material strips according to the invention include plastics,
Organic glass, especially flat glass.

Since flat glass is manufactured mechanically in large quantities in the form of endless sheets, it is natural that efforts are made to minimize the source of defects, and as a result, the requirements for inspection equipment are increased when manufacturing flat glass. is large. Therefore, although the invention will be described with respect to the example of flat glass, the invention is not limited thereto.

For example, when manufacturing flat glass on a 70-gaze machine, even with the greatest care, intrusion of mostly transparent fine stones into the glass strip still occurs. Another defect that is also frequent is air bubbles that are present in a fine distribution in the melt. These two types of defects, when reaching a certain size, cause surface deformation of the glass strip even if it is completely enclosed by the glass. However, surface deformations can be detected very well by electro-optical inspection devices and methods, such as those described, for example, in DE-A-2411407. However, this is not the case if the defects are small enough not to change the surface of the glass strip, especially in the case of microscopic internal bubbles (Kernblases);
If it is not OO'16 clean, it will not be detected by conventional equipment.

Inspection of float glass is carried out by scanning the entire width of a continuously moving strip of material with a moving light spot. This moving light spot is generally generated by a laser emitting device to obtain high brightness, but when the device is directed at a rotating metallized polygon, the light beam is delivered at high speed as a result of the high number of turns of the polygon. Creates a moving light spot as it moves across the flat glass. A part of the light ray has already been reflected on the glass strip surface, another part enters into the glass strip and is reflected by the lower surface of the glass strip, and most of the light ray passes through the glass strip after refraction.

Defect inspection devices of the type described in DE-A-2411407 use a moving light spot to scan surface defects over the width of a strip of material, usually moving at relatively high speeds. In the case of transparent materials, the inspection device has an adjustable sensitivity which makes it possible to detect defects on the top side as well as on the bottom side by scanning the material strip from above.

In this case, the internal bubbles and fine inclusions contained in the IJ tube do not refract light as strongly as surface deformations do, i.e. the signal formed by these defects is It is as weak as the signal formed by the fine dust particles present on the strip. However, these signals 2 are cut at the evaluation station of the inspection device, and the cut limit value can be adjusted by the signal height. Sensitivity is therefore reduced until surface contamination no longer forms a defect signal.

However, if internal bubbles or microstones are included in the glass strip, the incident light spot is refracted in the bubbles or at the surface of the microstones and continues to be guided through the material strip. In this case, the material strip itself thus acts as a light guide. The internal bubbles, i.e. microbubbles and contained microstones, have a roughly spherical shape, so that the light rays incident on them, depending on their lateral movement and thus on the variation of the angle of incidence, are at least once parallel to the scanning line in the material strip. and thus reaches the right or left side edge, where the ray becomes visible as a bright spot of light that shines for a short time.

However, in this case no information about the defect itself can still be formed, ie the extent of the defect cannot be indicated by a light spot shining on the side. It is therefore also not possible to determine whether the material strip must be separated or whether the same strip can still be used because the degree of defect is minimal.

``However, all transparent materials absorb a certain portion of the light that passes through them. In other words, the width of relatively wide flat glass strips often exceeds 3 m. So-called internal bubbles, i.e.
At the appearance of a bubble in the center of JT, the light reflected from this bubble has to travel approximately 1.50 m on either side before reaching the phototube, typically a photomultiplier tube. Without this resulting in significant light absorption, ie an additional strengthening of the light emitted by the photomultiplier, it is not possible to give accurate information about these detected defects. On the other hand, the light beam is the material (IJ)
As we move to the edge of the IJ tube, if the extent of the defect detected and its location in the IJ tube is the same as the defect detected in the center of the IJ tube, then as we move closer to the edge, Gives an increasingly obvious defect signal. Furthermore, the strip of material to be tested, i.e. float glass, is never
Not 00% clean, in other words, there are dust particles on both the upper and lower surfaces of the glass, which can reflect light rays into the glass as well. That is, there is always a constant noise level, which also changes; in other words, when scanning at the center of the strip, the noise level is significantly lower than when scanning at the edge of the strip, so that the IJ block Defects present in the center fall within the noise level present at the edges of the strip. Therefore, by differentially suppressing the noise level and taking into account the absorption of the transparent material strip, a defect in the edge area of the material strip is exactly the same as a defect of the same kind and degree in the central area of the material strip.・It is important to try to give Zorusu.

It is therefore an object of the present invention to detect and evaluate defects in a transparent material IJ tube that do not lead to surface deformation of the material IJ tube. In particular, we detect so-called internal bubbles, i.e. bubbles that are present in the center of the IJ tube and are so minute that they are covered by a layer of material strips that is thick compared to their size, and that they are caused by absorption by the glass. It is to evaluate without influence.

The task is to inspect a transparent strip of material, especially flat glass, for defects such as foreign objects or air bubbles contained in the strip, by scanning the entire width of the strip using a moving light spot. The problem is solved by a method for inspecting transparent material strips, which consists of receiving transmitted and/or reflected light, converting it into an electrical signal and evaluating it, which method detects the light rays emanating from the sides of the strip during the scanning cycle. The problem is solved by additionally detecting the voltage, converting it into an electrical current, and evaluating the resulting voltage by its opposite polarity.

The light rays emitted from the sides of the strip are focused, converted into ξ las, and used to control the evaluation device. Localization 1- and its degree can be recognized.

Standard surface contamination of the material strip to be tested does not form a defect indication.

All lateral electrical nodules ξ are scanned across the transparent material strip and, depending on the position of the moving light spot, are compared with a selectable value related to this position and, when this value is exceeded, a defect signal is detected. works.

Advantageously, the selectable values are stored in an electrical memory device. This implementation is particularly advantageous if only one material, eg one type of glass, is to be tested, so that the material strip does not change at all in composition and thickness. In this case, it is sufficient to describe the absorption curve of the material only once and to memorize it.

The concept of electrical memory devices is semiconductor memory devices, which vary depending on the circuit technology used.

RAM or ROM or FROM in addition to shift register
A memory device such as PROM5 (Programmable read
onlymemories) are particularly advantageous. This PROM 5 is a fixed value memory device which, depending on the manufacturing process, has, for example, a certain combination of pit-patterns desired in a semiconductor circuit. This programming can no longer be undone. In other words, after activating the FROM, it is impossible to change the changed information, thereby making unintentional changes in the test state impossible.In the second, programmability of the PROM5, , taking advantage of the capacitance of highly insulated gate electrodes.

This capacity can be discharged by irradiation with UV light and recharged, ie programmed, by applying a correspondingly high voltage.

The logic of the evaluation unit is to compare the incoming ξlux value with the stored ξlux value corresponding to the respective scanning position of the scanning beam, and to signal a defect when the stored pulse value is exceeded. issue. Of course, it is also possible in this case to operate a number of PROMs 5 corresponding to different curves. In other words, it is possible to test various material strips after preselection of a suitable memory device. In this case, as a memory device, RAM 5 is also advantageous since it does not have the ability to hold stored data for a long time, but can be programmed arbitrarily.

When a material strip does not have these defects, at each position of the moving light spot on the IJ tube, a . ξ Lus is the same at the same position of the moving light spot. In this way, the .xi. rus values are canceled out in a defect-free state. In other words, no runout occurs at all, but if there is a defect,...
Differences occur between the error values. Since the absorption of the glass is blocked by the opposite polarity of the obtained voltage, the size of the defect can be deciphered by the size of the difference in ξ Lus. In other words, defects of the same size will give a defect signal of the same size, regardless of their location, ie, regardless of their distance from the edge of the material strip.

The evaluation of the lateral direction ξ is based on the trigger limit (Triggers-
ChwellB) is advantageously used. For this purpose, the absorption curves are stored in a PROM, which allows the evaluation to be carried out very precisely. With this method it was possible to achieve a method that is completely independent of speed and has no excess vibrations. By including many PROMs 5, it is also possible to program the inspection of colored glass.

The invention will be explained in more detail with reference to the accompanying drawings.

The accompanying drawing is a schematic perspective view of the inspection device.

Next, the present invention will be explained in detail with reference to the drawings.

The material strip 1 is moved under the inspection device 2 by a roll 8 driven by a motor 9. The inspection device 2 includes a reflected light receiving device 3 and a transmitted light receiving device 3'. Both receivers are connected to an evaluation station, which station is also loaded by a photomultiplier tube 5' arranged on the side of the material strip 1.

A laser beam 14 arranged in the inspection device 2 forms a light spot 10 on a rotating mirror wheel 15 .

If a defect in the form of an internal bubble 13 occurs during the material step, the scanning beam 16 no longer becomes a reflected scanning beam 16'.
does not reach the receiver 3 and is emitted as a light ray 11 or 12 roughly along the scanning line 7 so that the material strip 1
from which the scanning beam enters a photomultiplier tube 5, 5' and the resulting pulses are transmitted to an evaluation station 4. Photomultiplier tube δ, 5' is cable 17
and 18 to the evaluation station 4. Similarly, an electric wire 19 extends between the light receiving device 3 and the evaluation stage 4.

[Brief explanation of the drawing]

The drawing is a schematic perspective view of an inspection device according to the invention. 1... Material strip, 2... Inspection device, 3, 3'
...Light receiving device, cow...Evaluation station, 5,5'
...Photomultiplier tube, 6...Side surface, 7...Scanning line,
8...Roll, 9...Motor, 10...Light spot,
12... Light beam, 13... Internal bubble, 14... Laser emitting device, 15... Mirror wheel, 16... Scanning beam,
17. 18... Cable, 19... Electric wire procedure amendment (method) November 11, 1980 To the Commissioner of the Japan Patent Office 1. Indication of the case 1988 Patent Application No. 131357 2
・Name of the invention Transparent Materials) IJ Tuzo's Inspection Method 3, Person making the amendment Relationship to the case: Patent applicant name Feldmühle Akchengesellschaft 4, Sub-Agent October 26, 1982 (Delivery date )6. Drawings subject to correction

Claims (1)

[Claims] l. In inspecting a strip of transparent material for defects such as foreign objects or air bubbles contained in the strip, the strip of material is scanned over the entire width of the strip using a moving light spot. , receives transmitted light and/or reflected light;
In a method for testing transparent material strips, which consists in converting and evaluating electrical signals, the light rays emanating from the sides of the strip during the scanning cycle are additionally detected, converted into electrical ξ lux, and lateral A method for inspecting a transparent material strip, characterized in that the inspection method is carried out using opposite polarities of voltages that have been evaluated for ξ rus. 2. The method according to claim 1, wherein the evaluation of the lateral and ξ lus is performed using a trigger limit.