DE2650706A1 - Automatic check of manufactured flat surface pattern accuracy - is by photoelectrically scanned comparison with master pattern and is esp. for banknotes - Google Patents

Abstract

The equipment is for fully automatically checking the accuracy of manufactured typically printed, patterns on flat surfaces by comparing them with a master pattern using a photoelectric scanning and storage technique. It provides more accurate and convenient operation than the existing semiautomatic optically aided methods of checking such patterns. Both the master and test piece patterns (3, 4) are laid on a movable table (5) driven by a motor (6) and shaft (7) past two long rows of photocells (1, 2) typically containing up to 1000 photocells each. The photocell outputs, are fed to storage registers which feed an electrically operated matrix representation of both patterns.

Description

Title: Procedure and device for automatic

Photoelectric implementation of the comparison of flat workpieces , printed sheets or certificates with a master sample.

Description of the Invention The invention is based on a method to carry out a coverage check by comparing a master sample with a flat individual item to be checked (workpiece, printing sheet, certificate, bank note i.a.) where the comparison is based on photoelectric scanning.

In practice there is a need for an automatic comparison in many places of flat workpieces, e.g. photographic or printing reproductions, Certificates and banknotes with a comparison standard, e.g. a master sample.

Today, such tasks are solved semi-automatically, e.g. by Simultaneous visual observation of the master sample and the test specimen using optical coverage methods. (State of the art) With high information content and poorly structured structures the workpieces to be tested (e.g. photographic or printing reproductions) one soon comes up against the limits of the safe, reliable and economical Feasibility of such comparisons, especially in the case of higher numbers of units workpieces to be tested. One is also when comparing original.

customers or cash bills are often automatically carried out from the outset the comparison instructed. However, there is no solution.

In the prior art, it is known to include the master sample and the test specimen to map photoelectric means linearly or planar in the form that over the course of a scanning process, the two objects (master sample and test item) the desired area is scanned photoelectrically with the required fineness will.

The grid-shaped picture elements converted into electrical quantities are electrically differentiated from each other in the event of deviations the electrical signals corresponding to the light impressions become the existing ones Differences counted as an error signal.

However, this method does not lead to any useful result the transitions between light and dark areas even with good grid accuracy again and again differences will arise, even if the agreement is within the framework the task at hand is satisfactory, i.e. there is no error at all.

The object of the invention is therefore to make a comparison with fotoeleki.

to be carried out automatically.

This object is achieved according to the invention by the features in the characterizing part of the claim 1 specified procedural steps (measures) solved.

A device for carrying out the method is constructed in this way that the coverage check of the master sample and the test specimen is carried out in such a way that that in the electrical mapping one of the two objects to each existing Transition (light / dark) in a delimited area of the "electrical field of view" of the other object, the corresponding plane-related light / dark transition of the other Object is searched for.

This assigned transition (abbreviation: "Satellite") must include of the same valence (light / dark or dark / light) within one prescribed by the "Uector distance" lying within the tolerance range can be found.

An essential element of the invention is therefore the mapping of the Objects to be compared (master sample and test item) in the corresponding electrical Fields of view whose dimensions correspond to those of the specified tolerance range have to.

Each reference transition must be within its associated "corresponding" Field of view (whose center is assigned to the reference transition) find its satellite transition, which arises from the corresponding transition of the other object to be compared.

This evaluation is only carried out for those cycles for which the reference transition meets an edge criterion that states that the edge is on the relevant point approximately perpendicular to the selected processing direction runs. The processing takes place simultaneously (in parallel) in several arbitrary specified directions in the electrical fields of view, primarily in the Main directions. Organizationally, information processing is split up in different working planes X, Y, U and V.

The coverage check from the master sample to the test item can be used as a safeguard of the result by means of a counter-check, which is also carried out at the same time can be supplemented by the test item to the master sample.

An embodiment of the invention is described in more detail below show schematically: Fig.l the mechanical-optical structure of a device for Implementation of the automatic coverage control.

2 shows a block diagram for the masking, the comparison and the Error assessment of a limited electrical field of view with double imaging from the lines photoelectrically scanned from the master sample and the test item.

Fig. 3 is a schematic representation of the photoelectric scanning line 4 shows an illustration of the information processing directions X, YZU, U.

5 shows a light / dark transition perpendicular to a processing direction.

6 shows an undefined transition situation in the case of an edge profile tangential processing direction.

Fig. 7 an electrical circuit for detecting a light / dark (h / d) transition and a dark / light (d / h) transition between neighboring ones Sampling points on one of the coordinate grid lines of the coordinates X, Y, U, V, (as Element of the transition generator) Fig. 8 shows an electrical circuit for comparison from h / d - resp.

d / h transitions derived from the master sample and the test item are.

9 shows a geometrical representation of the conditions in order to be converted into a limited electrical field of view to detect an edge perpendicular to the X-axis, Fix.10 A circuit for detecting an edge (edge generator).

Fig.lla a secondary electrical field of view with the transition information for coverage control.

Fiq.llb a circuit of the satellite detector.

Fig. 12 shows an electrical circuit for comparing h / d transitions or d / h transitions, which have been derived from the master sample and test specimen, with cross-checking.

13 shows a circuit for summarizing errors.

In Fig. 1, 1 and 2 denote photoelectric diode cells having a A large number (e.g. 1000) of photoelectric imaging elements, (Fig. 3), which are placed on a A few centimeters wide the images projected on them of those below Convert objects 3, 4 into electrical signals and these e.g. using a built-in Output shift registers via their outputs 8,9.

Instead of rows of diodes, known types of optical / mechanical Scanners are used, for example, with rotating or oscillating mirrors, through which the optical signals are converted into serial electrical information.

In this way, the objects to be recorded (master sample 3, test item 4) futoelectrically scanned and converted into serial electrical information.

The photoelectric scanning can in a known manner with a visual comparator can be combined, whereby the coverage and alignment of the original pattern and test specimen can be produced to each other at the beginning of the scanning process.

The line-by-line electrical scanning, which in itself does not have any Imaging in an electrical field of view is allowed, is supplemented by a mechanical one Path advance of master sample 3 and test item 4 through a support table 5 of his Continuous feed from the drive motor 6 via a spindle 7 is received. Any other forms of mechanical feed generation are conceivable as well a transverse transport, not shown here, through which in a new path after Completion of a full trajectory scan, close the rows of diodes; a corresponding new one Path scanning can be initiated.

The shift registers of both scanning rulers are clocked synchronously with the ~ clock (T) -, so that the serial information occurring at the same time Corresponding signals at both outputs from those in optical coverage Objects (master samples, test specimen).

The transformation into a limited electrical field of view takes place with the help of runtime chains, e.g. shift registers, compare Figure 2.

In FIG. 2, lE; l2,14 denote runtime chains for the information from Master pattern, e.g. Shift register, the capacity of which corresponds to the number of steps in the diode row corresponds to photoelectric scanning.

The information from the scanning of the occurs in the shift register 10 The maturity chains are connected in series and at their ends directly or (as shown here) through shift registers 11, 13, 15 with parallel outputs tapped.

The information at the outputs of the shift registers 11, 13, 15 are shown in the geometry of an electrical field of view 22. The symbolism this illustration is used for the convenient explanation of the geometrical-electrical relationships however, not an object of the invention. The electrical field of view is used as a switching value divider to be understood for the distribution of the incoming and outgoing The primary field of view contains the primary information (bright, dark), secondary fields of view contain secondary information, such as transitions. The field of view 22 comprises, for example, 3 × 3 grid lines with primary information.

The electric field of view 22 thus forms a large area on one narrow district 3 grid lines of the optical image of the scanned object (master sample ) from, being an essential facial point in the context of the present invention consists in that all the captured pixels in the way through the field of view "clocked through", that each pixel is once in the center of the electrical Field of view 22 is located.

The same arrangement is made for the other object (here the test item) with delay chains 16, 18, 20 and shift registers with parallel outputs 17, 19, 21. In this way, the electric field of view 22 contains an electric double image of master samples and test specimen that are covered, namely to the extent of 3 grid lines. (electrical double field of view) By appropriate arrangement The number of the grid lines of the electrical field of view are further increased, as far as this the uniqueness of the assignment of satellite transitions within the framework of the existing one Object grid permitted.

To the electrical double face field (intended as a switching point) 22, which still contains the original primary image information, is according to the invention an error detection 23 is connected.

In this error detection 23, the following operations become one by one or carried out in their entirety: a) light / dark (h / d) and dark / light (d / h) transitions identify and evaluate.

b) Carry out a coverage check from the master sample to the test item.

c) Carry out a counter-check from the test item to the master sample.

The search for corresponding transitions cannot be done indiscriminately for every transition that presents itself takes place. The structure of the electric field of vision 22 in Figure 2 suggests that the transitions in the direction of the main coordinates (x, v) Because it is always an operation on the standing visual field (a situation, each for times in the order of magnitude of one microsecond may be given) so one can determine the direction of the grid lines in which the transitions are to be formed arbitrarily, e.g. in the direction of the image scanning (X) resp. of the image transport (v) define Fig. 3. (also opposite. directions can are defined as directions of progress.) In addition to the existing two main directions (X and Y) can also be any secondary directions as advancement directions for the Transition formation can be defined, see Figure 4, with the entered secondary directions U and V with X and Y as main directions. It should also be explained with regard to FIG. 4 that the weak delimit a square field with the same hatching on each of the marked lines, encompassed by a scanning photo element.

The strongly drawn out network represents the effective scanning lines, i.e., the connecting lines of the switching points of the photoelectric scanning.

In which of the possible directions the d / h or h / d transition to with which the search process is to be carried out (reference transition) depends depends on the direction of the edge at the relevant reference point or the contour whose Coincidence with the contour of the corresponding transition is sought. A reference transition namely, the search is to be carried out in a scanning direction that is (ideally) perpendicular to the direction to be scanned Edge lies, compare FIG. 5. Then the results are clear for the master and the test specimen neighboring transitions of the same valence (light / dark resp.

dark / light), in contrast to the unclear conditions in "Schrammender" Scanning direction, see Figure 6.

So there is one transition for every transition, depending on the position of the edge to be scanned assigned to a certain direction, whereby the transition is conditionally given a vector character. Strict adherence to the transition direction is not required, the edge criterion can therefore be kept quite imprecise, but scratching transitions can be ruled out.

So the rule in the context of the invention is that the transitions .are to be provided with edge directions as a matter of principle, provided they are used as reference transitions should be evaluated (edge criterion) Since the implementation of the edge criterion means additional effort for the purpose of determining the direction for the transition, endeavors will be made to limit this operation to what is absolutely necessary. So it is sufficient if the edge determination is only applied to the reference transition, by relying on the satellite to have an approximately similar one Edge progression is present (or there is no satellite at all.) Through the introduction of transitions (h / d; d / h), adjacent scanning information is converted into different organizational levels relocated.

This is an advantage because of the distribution of: Information a dilution of the dense information on different processing levels Occurs at each processing level.

In addition, the introduction of "transfers" takes the place of direct light or Dark information does not result in any loss of information.

Various couches can be used to implement the procedure depending on whether the execution of the operations to be performed for the different Editing levels are carried out using a simple hardware logic, or in the familiar Time division multiplexing, with multiple use of the existing ones logic for data processing in the various work levels, or whether data processing by using a freely programmable computer. Essential in the sense of the invention is in each case the assumption of an evaluable reference transition, the belongs to the one of the two objects that was raised as a reference and that in a limited individual field of view of the corresponding object after a Satellite crossing is searched, then in the event that the satellite crossing is found in the relevant field of view, the result of the coverage check for this point is considered positive.

The realization of the transition formation is the example of a simple one Logic explained for a single organizational processing level, whereby according to the invention the processing for each scanning direction (X, Y, possibly also U and V) to be carried out has, so that after the subdivisions into the valences h / d and d / h, a total of 4 Up to 8 organizational levels, data processing is to be carried out to the same extent Has.

The realization of the transition formation without edge direction control Figure 7 shows.

The operation mentioned is a "self-operation" on the master or the unit under test, and only at the relevant organizational level, compare truth table FIG. 7a, and both valences of transitions (h / d; d / h) are obtained at the same time.

7b shows a logic circuit with which d / h and h / d transitions can be recorded. This circuit consists of two AND gates 24, 25, with each toei inputs and each to one output A1, A2. The inputs E1, E2 of the logic circuit are each with an input of an AND gate 24,25 and with connected to the negated input of the other AND gate 25,24.

Gen inputs El and E2 receive information from in one of the directions X, ~ Y, U or V adjacent connections of the electrical field of view fed. A determined h / d or d / h transition should - by definition- can be located at the input with the higher index, according to the example below Fig. 7c thus at n + 2, provided that a transition was found between n + 1 and n + 2. Others Assignments are possible.

The operation mentioned must therefore apply to all in the processing direction successive pairs of elements are executed. Under consideration of double valence (h / d; d / h) and a maximum of 4 levels (X, Y, U, V) depending on the desired Degree of the edge direction division must be the operations in 2 respectively. 4 levels be performed.

A corresponding number of n x n individual elements of the transition formation is to be provided for an electrical field of view of n x n grid lines per coordinate.

The totality of the required transitions in one processing level forms a transition generator 1 '28 or 32 (Fig. 8).

The overall arrangement of the coverage check is shown in FIG. 8.

The individual fields of view 27.3l of the electrical double field of view 22 are shown in Fig. 8. They provide the primary information for the transition generators ? 8, 32 and these in turn the signals for the satellite detector 29 of the correspondent, as well as the edge generator 33 of the reference. The latter provides by forming the edge criterion determines whether it is a valued transition within the meaning of the present definition acts, which can thus be raised to the reference transition.

In contrast, it is determined in the correspondent's satellite detector 29 whether there is at least one grid line in the correspondent's field of view a satellite is located. A single satellite is enough for a positive result of the Coverage control.

If an evaluated reference transition is reported by the edge generator and if the satellite detector shows the message "Satellite available, so reports the coverage control continues the positive result of the control over its outcome.

A schematic example of the formation of the directed transition Fig. 9 shows.

II The network of lines in FIG. 9 contains an h / d- or d / h information for a processing direction in which an edge is detected shall be. The verification is therefore only carried out for VI the reference point U, which is the relevant reference edge at one point, and it is only in the relevant one In each of the two adjacent to the central network line Lines must be a transition in the indicated area a to p per (horizontal) line exist (and only one), otherwise the edge criterion is not met.

Shapes with smaller dimensions in both coordinates are conceivable and are part of the invention.

FIG. 10 shows a corresponding implementation example of the edge generator. Each of the 4 exclusive OR gates 34 to 37 detects the inputs of a raster line. All inputs at AND gate 38 must be occupied so that the transition is evaluated will.

In the case of non-evaluation, the transfer can not be a cover operation cause.

If the edge criterion is not clear, for the same reference point multiple directions are evaluated (which only increases the redundancy of the. system will) "Schrammends" transitions, on the other hand, are definitely suppressed.

An exemplary embodiment of the satellite detector for a transition field of view of 7 x 7 grid lines, compare Fig.lla.

For the sake of simplification (as already pointed out became) unevaluated transitions processed because the evaluated reference transition already has a provides a good guarantee that the satellite transitions are also in order. It can also be evaluated from a whole field of transitions in the satellite domain can be assumed.

There may only be one transition on each of the grid lines. This is monitored by the exclusive OR gates 38 to 44 (Fig.llb) the inputs of each of these exclusive OR gates, e.g. 38, with the information of a Raster line, e.g. a to f, of the transition field of view (Fig.lla) acted upon The transition field of view represents the output of the transition detector 32 (FIG. 8) The exclusive-OR gates 38 to 44 are followed by an OR gate 45. This means: at least one of the network lines evaluated in this way fulfills the exclusive OR condition, then the OR gate 45 emits the "satellite present" signal at its output.

An embodiment for a complete coverage control with Countercheck is shown in Fig. 12.

The circuit shown as a block diagram in FIG. 12 results from the circuit of Figure 8 by the transition generators 28, 32 each one Edge generator 33 or 46 and a satellite detector 47 or 29 are connected downstream There are also - as in Fig. 8 - an edge generator 33 or 46 and a satellite detector each 29 or 47 connected to a coverage control 30 or 48 on the output side.

The mode of operation is in each case the same as in the figure above 8 for simple coverage control.

The cover checks or Cross-checks are carried out in several processing levels carried out in parallel (or in time division), or by means of a freely programmable one Computer in which the functions mentioned are programmed.

The results of the coverage check from the various (organizational) Processing levels can be evaluated individually and output separately as errors will. In addition to specifying the relevant (organizational) processing level (e.g. X, h / d) the determined vector distances are given, for example.

These can also be summarized statistically by counting.

Another form of error presentation is the organizational Original plane - not passed on, but for a specific edge point the errors of the totality of the processing levels are summarized before the transfer, according to their affiliation to a single (same) edge point, compare Fig. 13.

Each error is based on the sampling rate and taking into account the runtimes in the data processing clearly to its place of origin on the relevant object and is in this way with the coordinates X and Y of the Scanning process output addressed, see Fig. 13th

In Fig. 13, an example of a downstream summary which forms error signals, the signals from all processing levels appear at the input, no. 1 to No. 8. (Coordinates X, Y, U, V in each the valences h / d and d / h). 8 such Signals come from the coverage control (additional character K) and 8 other signals come from the counter check (additional character G) All receipts from the cover check are switched to the OR gate 51 and are summarized in this. as well the input signals of the countercheck are switched to the OR gate 53 and are summarized in this.

The outputs of the OR gates 51 and 53 are inverted to one of the AND gate 52, 54 switched, on the other input of which the combined evaluated Transition signals from control (on 52) and counter-control (on 54) act. These AND gates provide additional protection and only then allow error signals if there is actually a reference point in the relevant cycle. the Forwarding to the error memory takes place in combination with an address specification, the is obtained via the delay chain 49 and the address counter 50.

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Claims (19)

Method for carrying out a coverage check by comparing a master sample with a single flat piece to be checked (Workpiece, printing sheet, certificate, bank note, etc.), whereby the comparison is based on a photoelectric scanning takes place, characterized in that the image of the piece to be tested is carried out in an electrical field of view in such a way that that in its central imaging point (reference point U, see Fig. 2) one after the other in the course of the scanning operation, each pixel of the master sample and / or of the test piece appears, and that the presence of congruence under admitting a defined vector distance between a reference transition (U), light / dark or dark / light, and the corresponding transition, light / dark or dark / light is controlled and in the case of the absence of the corresponding Transition within this distance an error signal is generated and output. 2. The method according to claim 1, characterized in that as reference transitions, from which the existence of corresponding corresponding transitions for the other object is to be determined, such transitions are used which the direction of the transition formation with a rough approximation with that to the relevant edge point corresponding normal direction of the edge. 3. The method according to claim 1 oder'2, characterized in that as corresponding transitions in the search process likewise transitions with directional evaluation be used. 4. The method according to claim 1 or 2, characterized in that also when recording corresponding transitions of transition information is assumed without special directional evaluation. 5. The method according to claim 1 or one of the following, characterized by that the directional evaluation takes place on mutually orthogonal grid lines, whereby the Direction criterion restricted to the approximation of these two main directions remain 6. The method according to any one of claims 1 to 5, characterized in that Direction criterion is extended to scan lines (processing directions U, V), the one that is orthogonal or oblique-angled rotated to the main directions (X, Y) Form a coordinate system. 7, the method according to any one of claims 1 to 6, characterized in that the transitions are formed by hardware or software operations, as the result of which is a certain type of signal with unchanged pixel content (light, dark) appears (e.g. zero), and that when there is an h / d transition as a separate Result a corresponding signal appears, as well as that at the edge transition d / h another corresponding signal appears as a separate result. 8. The method according to any one of claims 1 to 6 ', characterized in that the edge direction criterion is formed by hardware or software operations so that when there is complete or approximate parallelism of the edge direction with the direction of formation of the transition, the generation of the edge information signal is suppressed. 9. The method according to any one of claims 1 to 8, characterized in that that belong to the hardware or software-related determination of the reference point corresponding transitions the control is carried out so that determined whether on at least the coordinate lines (X, Y, U, V) of the field of view and there is only one transition, and that if at least one is present such a transition forwarded a corresponding message to the coverage control will. 10. The method according to any one of claims 1 to 9, characterized in that the simultaneous presence of a korres-1? ponding transition and one evaluated reference transition with means of the hardware or software Logic is recorded, and the positive result of the coverage check as a good criterion is evaluated respectively. the lack of coverage confirmation as an error signal is output when the reference transition is present. 11. The method according to any one of claims 1 to, characterized in that the coverage check is carried out for all processing levels, namely the Coordinate axes x (h / d, d / h) Y (h / d, d / h) and possibly also U (hJd, d / h) and U (h / d, d / h) and that the negative results of the coverage check for the error signaling can be used. 12. The method according to claim 11, characterized in that the errors all organizational processing levels X, Y and svt. also U and V combined with which all errors related to a single edge point can be summarized and output regardless of their original level. 13. The method according to any one of claims 1 to 12, characterized in that that the control carried out from the master sample to the test item is carried out by a counter-check is supplemented by the test item to the master sample. 14. Arrangement according to one of the methods according to claim 1 or one of the following, characterized in that the electrical fields of view (22) for master sample (3) and test item (4) through runtime chains in the form of shift registers (10,12,14,16,18,20) the same number of steps as the diode chains of the scanning lines (1 , 2) from the serial information of the scan lines as an electrical map a limited part of the original field of view by means of accessible parallel exits a smaller number of shift registers (11, 13, 15, 17, 19, 21) are generated, and that the double field of view (22) is followed by the error detection (23) (Fig. 2) 15. Arrangement according to claim 14 for performing the method according to claim 7, characterized in that in the error detection on the input side in at least a transition generator, (28, 32) a logic circuit is provided which its basic principle can be traced back to two AND elements, each of which is two Have inputs and one output each, each with an input one AND circuit and connected to a negated input of the other AND circuit is (Fig.7) 16. Arrangement according to claim 14 or 15 for performing the method according to claim 10, characterized in that in the error detection (23) one Transition generator (2s) a satellite detector (29) and this a cover control (30) and that a further transition generator (32) an edge generator (33) and This may be followed by the coverage check (3 0). 17. Arrangement according to claim 14 or 15 for carrying out the method according to claim 13, characterized in that in the error detection (23) each transition generator (28, 32) a satellite detector (29, 47) and each an edge generator (33, 46) is connected downstream and that two coverage controls (38, 48) are provided, the inputs of which are each connected to the output of an edge generator and a satellite detector are connected. 18 The arrangement according to claim 17, characterized in that the results the coverage checks are used to report errors as the final result of the scanning process will. 19. The arrangement according to claim 18, characterized in that the affiliation of the error is output at a certain point of the associated device under test, by corresponding to the timing of the image information on the addressing coordinates the error is inferred.