EP0053151A1

EP0053151A1 - Optical control method for controlling the quality of transparent articles and apparatus for implementing such method

Info

Publication number: EP0053151A1
Application number: EP81901533A
Authority: EP
Inventors: Peter Hermann
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-06-16
Filing date: 1981-06-12
Publication date: 1982-06-09
Also published as: IT8122337A0; CH652826A5; IT1138411B; WO1981003706A1

Abstract

Des felures et d'autres defauts dans des verres seront detectes lorsque des rayons visibles ou voisins du spectre visible sont devies ou reflechis. D'apres le procede selon l'invention, les sources et detecteurs optiques sont disposes de maniere classique. Pour obtenir un rapport optimum entre le signal utile et le signal disperse, certaines relations geometriques sont utilisees. Dans l'appareil selon l'invention, on dispose des groupes detecteurs en relation avec les sources de rayonnement. Ces groupes sont, en ce qui concerne la technique des signaux, independants grace a un systeme special multicanaux. Une installation de test complexe sera reduite a un certain nombre de systeme partiels faciles a regler. De la, il resulte une economie de moyens lors de l'installation, des meilleurs resultats, une reproductibilite et une standardisation de la construction.Cracks and other defects in lenses will be detected when visible or near visible rays are deflected or reflected. According to the method according to the invention, the optical sources and detectors are arranged in a conventional manner. To obtain an optimum ratio between the useful signal and the dispersed signal, certain geometric relationships are used. In the device according to the invention, detector groups are available in relation to the radiation sources. These groups are, as far as signal technology is concerned, independent thanks to a special multi-channel system. A complex test setup will be reduced to a number of easily adjusted partial systems. This results in a saving of resources during installation, better results, reproducibility and standardization of construction.

Description

Title: Process for the optical monitoring of the quality of transparent bodies and a device for carrying out the process

DESCRIPTION

Technical field of the invention

The invention relates to a method for the semi-automatic or fully automatic quality inspection of transparent media, in which the change in a beam path through the interference points is used to detect them, and a device (device system) with which

With the help of this method, it can be carried out economically, but which device can also be used with advantage in more conventional methods of optical quality testing and in principle in analog optical methods. State of the art

A special application of the method and the device lies in the testing of glasses, especially hollow glasses, which are checked for cracks and other defects. Originally, the optical crack test method, which is mainly dealt with here, was based on a highly variable, individual arrangement of a plurality of lighting bodies of the same type and a number of individual detectors, only by their sensitivity, which is usually relatively undefined solid angle zones Secondary beam detected and which reacted to all radiators of the same ace. It is still the most common method in production control today. If you want to achieve reasonably acceptable results, long and tedious adjustment work by experienced, qualified employees is necessary for every type of test work and the amount of equipment increases enormously with the requirements.

The crack test based on total reflection was extremely complex in previous application technology

Method. Cracks occur on the hollow glass in all areas of the container, such as the mouth, shoulder, body and bottom; albeit with different distribution. Roughly one speaks mostly of horizontal or vertical cracks. However, there are various inclined positions as well as twisting of the crack surfaces. The main orientation of a crack can be defined by 2 angles. Numerical evaluations by computer simulation on the basis of areas which can cover these angles show that a good crack check is only possible if several, defined and relatively large angle zones can be formed on the detection side, which have no mutual influence ¬ solution work independently. This is the only way achievements can be achieved which give optimal results on a statistical average. This concept was not realizable with the previous apparatus. Existing solutions, in which the measuring apparatus is distributed over several stations arranged one behind the other, are a first, but complex step to separate detection areas.

If you point a spotlight at a glass, certain areas are always brightened so strongly that crack detection can no longer be carried out there using conventional methods. However, certain zones of _. a sum of scattered radiation, which is weaker in itself, is lightened too much (cumulation). This problem is exacerbated by the fact that these scattered rays occur very differently from glass to glass and change even more with the type of glass (seams, threads, etc.).

Another disturbing effect is the change in the light when working with visible rays. Compensating for this effect by adjusting the sensitivity is not a viable option.

Various improvements have become known. In order to eliminate the disturbing influence of scattered rays on certain detectors, radiators with different colors or with the same type of radiation but different modulation frequencies are used. The method partially simplifies the setup of a test head, but is limited in terms of expenditure (FR-PS 1 588 308).

Certain improvements in the results, above all by suppressing the scattered light, are achieved if the detectors do not react to absolute values, but to -

OMPI the rate of change of the beam. However, the method is only partially effective since scattered lights are also modulated.

In practice, the need has arisen to place radiators and detectors at a greater distance from the measurement object in order to improve the space available, to make the device less dependent on the position accuracy of the measurement object and to improve the ratio of useful signal to interference signal. (In most cases, the scattered light decreases quadratically, while the useful light in certain areas decreases linearly with the distance.) In conventional systems, however, a small distance is unavoidable (detection angle range, scattered light accumulation, mutual influence of different arrangements).

The many difficulties have led to the fact that the test heads, which have been built with a lot of effort, are very individual and make it impossible to standardize the arrangement. A partial solution for standardizing the structure gives the following method. Fixed sub-units with emitters and detectors can be suitably joined together as building blocks, which reduces the time required for the installation. The space problem is only partially solved (DE 28 02 107 AI).

Invention The present invention goes in detail and in the conception new ways to substantially reduce the above-mentioned problems with the aim of reducing the outlay on equipment and increasing the test quality and also includes the necessary equipment with which this (and analog) Process can be carried out economically. The method according to the invention assumes that a beam emanating from an emitter irradiates a measuring point on the measurement object in the appropriate form. If there is a disturbance at this point, in the case specifically described here, a crack, a reflected beam is thrown from there into a limited solid angle range. The method based on the fact is arranged that in a relatively large distance from the measurement object door surface a standard stocked Detek¬ which stanchions without mechanical Verände-, can be divided by programming in detector zones which cover enough ^'room angle to cracks with certain Capture orientation and location. From the point of view of signal technology, several independent systems, each consisting of one or a few emitters and a detector zone matched to the emitter and crack, can be formed. A single detector-emitter system is each intended for a (possibly a few) measuring zone on the glass and for a limited range of crack angles. The superimposition of several such systems then leads to a complete inspection of the measurement object. The measuring zones of the different systems can partially overlap, which results in multiple use of the mostly standard arranged detector elements. The sensitivity can be changed within a zone. Surface elements that belong to different systems at the same time can adopt an optimal sensitivity for each system separately by programming.

The result of this method is that a complex measuring apparatus can be subdivided into a number of subsystems that can be set easily and independently of one another. Illuminations which have arisen as a result of the necessary radiation in one system are ineffective in other systems and there is no accumulation of scattered light.

VflΫO The enclosed figures show:

Fig. 1 beam path and detection area;

2 projection of a crack in the glass into the detection area, with detectors;

3 shows some beam paths with emitters and detector blocks during the inspection of cylindrical glass containers;

Fig. 4 signal block diagram of the electro-optical device system.

The embodiment shown in FIG. 1 shows a cylindrical glass body 1 with a crack 2, which reflects 5 the beam 4 emanating from the radiator 3 and throws it onto the detector surface 6.

In automatic test systems, there is usually a shift (or rotation) between measurements

Test object and measuring device instead. To simplify the apparatus, this can be used in such a way that the detection surface 6 in FIG. 1 is not completely occupied with detection elements, but rather is reflected only on strips 8 transverse to the direction of movement of the reflection point 9 of the

Beam. Such detection strips are summarized in terms of apparatus in detector blocks 7, which are connected to the evaluating device.

A large number of emitters are normally used to adequately detect different types of cracks at different locations, which in turn can be arranged regularly and in a standardized manner. The sy In accordance with the invention, system separation is carried out using a sequential method, ie all elements belonging to a subsystem are activated simultaneously for a certain time interval in a sufficiently rapid sequence, but different subsystems are never activated at the same time. In addition, the response sensitivities of a detector can also be selected differently depending on the subsystems in which it works, ie it has quasi different system-related sensitivities at the same time. The device is provided with memories in which the assignment of the detector elements to the different systems and the different sensitivities of the detector elements in the different systems are programmed. Programming can be carried out with buttons or with a data carrier (punch cards, punched tape, magnetic tape, magnetic disks) which is customary in data technology.

If a device is sufficiently equipped with emitters and detectors, it is possible to adapt a measuring device to a certain type of glass practically exclusively by programming. This opens up the possibility of generating the programming semi-automatically (interactively) or fully automatically. A small computer determines e.g. the assignments and sensitivities in a learning process with good and faulty glasses.

In order to achieve channel separation, the emitters of the individual systems are periodically briefly switched on (pulsed) at certain time intervals. See 42 of FIG. 4 for this. During the on period of the emitters of a system, the detectors assigned to this system are activated and measure the increase in radiation compared to the time before the emitters were switched on. If the

ΓOREX

OMPI If the value specified by the programming for this system and the corresponding detector grows, a corresponding signal is forwarded to the evaluation logic, which effects a necessary action (display, ejection of the glass). The evaluation logic can make an action dependent on further information (for example, designation of a glass). The evaluation logic can be expanded as required (e.g. small computer), evaluate the data statistically and forward them in a suitable form.

The specified type of channel separation also results in a very strong suppression of radiation which results from the environment, even if this radiation is not constant over time (e.g. fluctuations of 100 Hz in the case of incandescent lamps)

Another component of the present invention is the relationship between the distance between the detection elements and their size, because it enables a better distinction to be made between reflecting or refractive zones and scattering zones. The signal-technical system separation provides the necessary prerequisites for choosing a suitable distance. 2, the surface 21 is exposed to a uniform interference or scattered radiation, in zone 22 the brightness is determined by a useful signal, e.g. the radiation reflected by a crack with a curvature is increased approximately uniformly. In this situation it is clear that the ratio of

Radiation intensity on detector 23 in detector block 7 z is the greatest on detector 24 when detector 23 is completely in zone 22. Thus, the distance of the detectors from the radiating point should be at least so large that it can be completely immersed in the diverging beam of the signal. Of course, this effect can only be fully

OI be used if the detectors have separate signal paths up to the response threshold. This method achieves a maximum useful / interference signal ratio for a given radiation. In the example of FIG. 3, a cylindrical hollow glass 31 rotates around the axis 32 during the test. The opening zone is irradiated by the emitters 33 and by the emitter 34 by means of reflection on the inner wall. Radiators 35 and 36 irradiate a deeper lying zone from different angles in such a way that as far as possible all occurring cracks throw evaluable bundles of rays into the cylindrical detection area. 38 and 39 are possible axes for detection cylinders which are occupied by detector blocks 7. Typical beam areas of the reflected useful signals are indicated by the line pairs 33 and 37, the areas belonging to 33 and 37 belonging to different independent subsystems.

4 ^' shows the signal block diagram of an exemplary embodiment of an electrical device for carrying out the method. A clock oscillator 41 drives a coding logic 42 which, on the one hand, emits the time-staggered pulses for the power amplifiers 43 of the semiconductor infrared emitters with a wavelength of approximately 0.9 μm for the radiators S1 to S16, and on the other hand generates the associated system code 44 for activating the detectors in the detector blocks 7, which are each equipped with 8 detectors D1 to ~ D8. The repetition rate is 1000 / s, with a switch-on period of the emitter of 5 us. After passing through the measuring zone, the emitted radiation 55 is received at a wide angle by the sensitive semiconductor detectors 45, converted into an electrical signal, filtered and amplified. The subsequent stage 46 compares this with an analog signal from the digital / analog converter 47, which depends on the system code and the programming from the selector logic gik 48 is controlled. The digital signals resulting from the comparison are selected in the selector 48 in accordance with the system code and the programming, reduced by OR circuits and then stored in the memory 49 until further evaluation. In one variant, the signals are already linked in the detector block 7 in order to save on connecting lines. In the evaluation part 51 (a micro-computer) the signals are stored, further reduced, evaluated and prepared for the displays on counters 55, lamp formers 56 and screens 53. The definition of the systems is done on a switch panel 50 performed. Alternatively, this preselection can also be input to the evaluation part 51 via a keyboard 54 or by means of one of the usual data carriers.

The cylindrically constructed spotlights 3 (see FIGS. 1 and 3) can be easily assembled and disassembled by means of a snap lock> and, for test purposes, replaced by spotlights with visible light which have the same beam geometry. The rays emanating from a semiconductor infrared emitter are bundled by means of a bi-convex lens in such a way that the imaging plane of the emitter lies further away than the measurement object and that a suitable cross-sectional area of the beam on the measurement object arises, which is approximately the same Lens cross section corresponds.

O PI IPO

Claims

P atentans Proche

1. A method for the detection of irregularities, imperfections, in particular cracks, in transparent media by optical means with emitters, detectors and evaluation, characterized in that the detection side and the emitter side are predominantly of a standardized design, ie that is independent of the exact nature of the measuring objects, a detection surface form suitable for a larger angular range, and in that separate ^(~ example, in the evaluation device such.) in a simple manner as well as adjacent and overlapping Detektionsfeider formed in this area and each of the radiators can be assigned such that a radiator / detector field system can act practically unaffected by another radiator / detector field system.

2. The method according to claim 1, characterized in that the detection area is resolved into a larger number of detection elements, the signal of which is processed separately to such an extent that the effect of the undesired scattered light which falls on different elements does not accumulate.

3. The method according to claim 1 or 2, characterized gekennzeich¬ net that the detection surfaces are predominantly flat, spherical or cylindrical and their distance from the DUT is at least so large that the individual detection elements with their active surface largely in the are able to immerse the signal beam emanating from the interfering point to be detected (and assumed to be diverging).

4. The method according to claim 1, 2 or 3, characterized gekenn¬ characterized in that, taking advantage of the fact that sic moves the beam to be detected (eg by rotation of the measurement object), the detection surface only in lines perpendicular to the direction of movement in the greatest possible distance from one another is provided with detectors, on the one hand to reduce the effort and on the other hand to improve the spatial conditions.

5. The method according to claim 1, 2, 3 or 4, characterized in that - the beam emanating from a radiator in a suitable area before and after the measurement object has the same, limited cross-section corresponding to the intended measurement zone (Circle, ellipse, rectangle), which has a uniform radiation density.

6. The method according to claim 1, 2, 3, 4 or 5, characterized ge indicates that the sensitivity of a detection element with respect to the different emitters, to which e can be assigned, can be selected differently.

7. The method according to claim 1, 2, 3, 4, 5 or 6, characterized in that the mutual assignment of detectors and emitters, as well as the setting of sensitivity using a connected data processing device partially or fully automated will be where compared with error-free and error-prone measurement objects.

8. The method according to claim 1, 2, 3, 4, 5, 6 or 7, characterized in that the distance of the detector surface from the measurement object is relatively large, ie several centimeters (typically 4 cm) is selected and the size and distance of the Detection elements are adapted to these conditions so that the following goals are achieved: better space for the arrangement of emitters and detectors; relative independence from the exact position of the measurement object; clear separation of the rays emerging at different angles; enough space for evaluation electronics at the beam detection point.

9. The method according to claim 1, 2, 3, 4, 5, 6, 7 or 8, da¬ characterized in that the automatic detection of the defects is carried out by means of an invisible radiation, but that to the structure, adjustment and transfer testing a system, a sufficiently exact equivalent system that works with visible light is used, whereby the detectors can be replaced by focusing screens.

10. Device with a plurality of signal-technically separated, open optical (light, ultraviolet radiation, infrared radiation) channels (corresponding to the emitter / detector field systems) for carrying out the method according to one or more of claims 1 to 9, but also more generally Can be used for measuring, testing and monitoring the shape, structure and position of objects, characterized in that the signal-technical separation of the detector-radiator systems is achieved by the channels or systems being successively and periodically in sufficient quantities short intervals.

11. The device according to claim 10, characterized in that ei¬ ne group of electronic, radiation-sensitive components combined with a signal preprocessing part in a movable block (several blocks possible), which are combined by a cable with the remaining parts of the device is connected.

12. The device according to claim 11, characterized in that there are signal comparators in the block, the comparison signal (threshold value) being fed in from the outside in analog or digital form.

13. Apparatus according to claim 10, 11 or 12, characterized in that the detection elements, individually or in groups, can optionally be assigned to no, one or more emitters to form signal-independent systems and that the sensitivity of one

Element can also be selected differently "simultaneously" in different systems.

14. Apparatus according to claim 10, 11, 12 or 13, characterized in that the beam emanating from the emitters maintains approximately the same properties over a relevant distance, e.g. round, elliptical or elongated cross-section. The cross-sectional area is selected in such a way that predominantly a limited zone suitable for the measurement is irradiated on the measurement object.

15. Apparatus according to claim 10, 11, 12, 13 or 14, characterized ge indicates that the emitters form compact, movable, connected with an electrical cable units, each containing a semiconductor emitter or that the emitter units with a Optical fibers are connected to a pulsed source (modulated laser; Kerr cell with constant radiation source; perforated disk with constant radiation source).

16. The apparatus of claim 10, 11, 12, 13, 14 or 15, characterized in that the assignment and evaluation of

O PI Radiators, detectors, sensitivities, etc. are carried out via a central logic (possibly programmable logic) and that assignments and signals can be viewed in a direct or evaluated form on a display device, or assignments can be defined.

17. Device according to one of claims 1 to 16, provided with a channel selector such that any subsystem can be selected therewith. that the majority of the controls (displays, buttons, etc.) only relate to this system.

OMPI