NO801128L - PROCEDURE AND DEVICE IDENTIFICATION DEVICE - Google Patents

Abstract

1. Method of identifying articles, which appear in any position and orientation and at any time at an image aperture and each have a designating area or panel on a surface which is facing the image aperture, which panel comprises symbols (52) in at least one datum track (51) and at least one contrasting line pattern (54), which characterizes the positon and the orientation of the datum track and has a plurality of parallel lines of different spacing and/or line width, in connection with which the image aperture is scanned line by line (60) and a binary video signal corresponding to the scanned contrast line pattern and the following symbols is produced, the image aperture in the first step of the method being scanned at different angles until a prescribed contrasting line pattern is detected, in the second step of the method, the position alignment of the data track relatively to the image aperture is established, and in the third of the method, a grid scanning is effected in the direction of the data track and the symbols are read off and decoded, characterized in that, - for the detection of the constrast line pattern (PIC), the interval lengths of overlapping intervals (Figs. 11 to 14) of the video signal and in each case comprising at least one light-dark region are measured and portrayed in the form of binary counter readings (TC1 to TC4), - that the counter readings (TC1 to TC4, Fig. 6) address a two-dimensional table (Fig. 10) which is stored in a store (28 in Fig. 7) and in which is contained an expectation zone with criteria for a prescribed ratio between two successive interval lengths of the intervals (11 to 14), - that the counter reading (TCN) corresponding to an interval length (IN) addresses one line of the table and the reading corresponding to the following interval length (IN+1) addresses one column of the table, - that a coincidence signal (LPIC1, LPIC2, LPIC3) is produced when the relation of the two respectively following interval lengths lies in a prescribed value range, and - that a recognition signal (PIC OUT Fig. 9) is delivered when a coincidence signal (LPIC1, LPIC2, LPIC3) is produced with a number of successive addressing steps which is prescribed by the contrast line pattern (PIC).

Description

The invention relates to a method and a device for the identification of objects that appear in an arbitrary position and orientation and at arbitrary times on a picture window and on a surface facing the picture window exhibit an identification in the form of a data field which in at least one data track includes contrasting characters with at least one contrast line pattern that characterizes the position and orientation of the data track and has several parallel lines with different distances and/or line widths, the image window being scanned linearly and a binary video signal corresponding to the scanned contrast sequence is produced, the image window being scanned in a first method step for as long under different angles that a contrast line pattern is recognized, and further the position and alignment of the data field in relation to the image window is determined in a second step, and a raster scan takes place in the direction of the data track and the characters contained in the data track are read and decoded in a third step.

Such methods and devices are already known. The objects to be identified are, for example, trade goods, department store articles or the like, which are identified in machine-readable form. For this purpose, identifications are affixed or placed on the objects or objects on which characters in a machine-readable code are printed, e.g. The OCR code. Such identification can consist of quality, dimension or price indications, of the article number, etc. This identification data is in one way or another placed on the objects' surfaces.

Such identifications can only be machine-read with difficulty, as the objects differ in size, and as these identifications e.g. on adhesive labels are placed in different places of the object. When reading the identification, one cannot therefore assume that it is available at specific times in a specific position with a fixed orientation. The "reading" of these identifications cannot therefore be compared to the reading of punched cards or the like in which a card is available in a precisely defined reading position at precisely determined times. In the present case, exactly the opposite is the case. The data field on the object only appears more or less approximately at a specific location, and also the alignment of the data field is relatively arbitrary.

Such methods and devices for identifying objects are e.g. used at checkouts in supermarkets etc., to enable automatic registration of the price and/or article number of the item that a customer wants to buy and has brought to the checkout for this purpose. The goods, such as boxes of different shapes and sizes, bottles, cartons, boxes etc., are then individually arranged on the image window, as only the surface that carries the data field used for product identification must be. aimed at the picture window. The data fields on the various objects thus appear with different alignment in different places within the image window. Furthermore, the data fields do not appear at fixed time intervals at the reading station. The reading station must therefore search for the data field and then read out the characters of the data tracks in the direction of the data tracks of the data fields. The characters read out can then be supplied as electrical signals to the till, which can print the price and possibly also the article number or the article group on the checkout slip.

The data field placed on the object is provided with a contrast line pattern (PIC) which comprises several parallel lines with different distances and/or different line widths. The contrast line pattern serves to highlight the data field, e.g. the printed label, in a reliable and unambiguous manner in relation to the other signs and line patterns that may be present on the object's surface in the data field's surroundings. With regard to the data tracks within the data field, the contrast line pattern also has a predetermined position and orientation and can therefore be used to determine the position and orientation of the contrast line pattern - and thus the data tracks - in relation to the scanning angle of the scan lines, and then in the direction of the data tracks to produce a scanning grid which in a vertical direction crosses over the characters within

the data tracks. The secure recognition of the contrast line pattern thus represents an essential step in the omnidirectional reading of such data fields which are printed with clear characters.

From DE-OS 2 338 561 there is known a method and a device of the type indicated at the outset, whereby the recognition of the contrast line pattern only occurs when the contrast line pattern is scanned essentially perpendicular to the direction of its lines and the pulse sequence thereby contained in the video signal is equal to a predetermined pulse sequence corresponding to the contrast line pattern used. It is thus a correlation method. It is a particular disadvantage here that the scanning of the image field for searching for the contrast line pattern must take place in very small angular increments until a scanning line intersects the contrast line pattern vertically, whereby the search time is undesirably long. Also, blurred printed edges make a<y>contrast line pattern's. lines are disturbingly noticeable and sometimes prevent a detected contrast line pattern from being recognized as such as the pulse sequence contained in the video signal deviates from the stored comparison pattern. As a result, either the search sequence is repeated or the contrast line pattern cannot be recognized at all, and the corresponding data field then remains unread.

The purpose of the invention is to provide a method and a device of the type indicated at the outset which enables quick and reliable recognition of the contrast line pattern and which works to a large extent unaffected by sharpness at the edges of the contrast lines.

According to the invention, the above-mentioned purpose is achieved by a method of the nature indicated at the outset in that the interval length of overlapping light and dark intervals of the video signal is measured for recognition of the contrast line pattern (PIC), that successively measured intervals are compared with each other and a comparison signal is produced with a first amplitude when the two interval lengths being compared are "in. a predetermined relationship to each other that corresponds to the contrast line pattern's corresponding distances, and that a recognition signal (PIC OUT) is emitted when a predetermined number of successive comparison steps is produced by one of the contrast line pattern a comparison signal with the first amplitude.

A device for identifying objects in accordance with the specified method comprises an opto-electronic scanning device which outputs a binary video signal which corresponds to a linearly scanned image field and consists of a series of light and dark intervals.

Such a device further comprises decoder devices for recognizing a searched contrast line pattern which characterizes the position and orientation of at least one data track of a data field and contains several parallel lines with different distances and/or line widths. The device further comprises devices for aligning the scan raster parallel to the data track and for reading the characters scanned with the scan raster from the data track. According to the invention, such a device is characterized by the fact that the decoder devices contain a counting circuit which receives the video signal and which counts the interval lengths of successively overlapping intervals of video signals, that the decoder devices contain at least one comparison table which, via a gate circuit, receives sequentially counted interval lengths in pairs and emits a comparison signal with a first amplitude when the two interval lengths compared with each other are in a predetermined mutual relationship which corresponds to the relationship between the corresponding intervals of the contrast line pattern, and that a utilization coupling is arranged which emits an identification signal (PIC-OUT) at an uninterrupted sequence of a predetermined number of comparison signals with the first amplitude.

The advantages of the invention lie in particular in that the recognition of the contrast line pattern only depends on whether the ratio between successive, mutually overlapping interval lengths of the video signal lies within narrow value ranges, so that the contrast line pattern also in a scan that takes place at an angle in relation to the direction of the contrast lines, occurs in a safe manner as the successively formed ratios between successively measured interval lengths of the video signal are invariant in relation to the scan angle. For reliable recognition of the contrast line pattern, it is thus sufficient to scan the contrast line pattern continuously - under an arbitrary angle - in which all contrast lines are completely crossed. The search for the contrast line pattern can thus take place in relatively large steps, i.e. relatively quickly.

As the decoding of the video signal for detection of the contrast line pattern with respect to the video signal must take place in real-time processing, i.e. essentially simultaneously with the production of the video signal, to ensure that a contrast line pattern is recognized at any location within the video signal, the determination of whether the ratio between continuously measured interval lengths lies within a predetermined value range, not by means of a division, but by input into a two-dimensional comparison table, also called a division table, which emits a comparison signal with a predetermined first amplitude only when both interval lengths compared with each other lie in a predetermined expectation field of the table within which the quotient between the intercompared interval lengths has a value range that corresponds to the value range for the corresponding interval lengths of the sought contrast line pattern. In this way, the time-

and hardware-consuming division method avoided and the real-time operation with respect to the video signal easily maintained.

The comparison table is preferably designed as two-dimensional non-volatile memory (PROM). The different possible discrete values of the first measured interval length address different lines or rows in the constant memory. The different discrete values of the subsequently measured interval length address different slots or columns in the constant memory. The expectation field is predetermined in such a way that it includes all the storage locations or memory cells in which the quotient between the interval length assigned to the line address and the interval length assigned to the column address lies in a predetermined value range. If a memory cell within the expectation field is addressed, the constant memory emits a comparison signal with a first amplitude which signals a recognition of the contrast line pattern.

If, on the other hand, the memory cell determined by line address and column address lies outside the expected field, a comparison signal with a second amplitude is emitted which signals that the quotient between the compared consecutive interval lengths lies outside the predetermined value range.

When a comparison signal with the second amplitude occurs, the decoder devices are then reset to zero and are then ready to carry out a new recognition and decoder step.

Preferably two and two interval lengths to be compared with each other are entered into a separate comparison table with a separate expectation field and there checked with regard to their quotient value. Each individual comparison table is preferably realized as a separate non-volatile memory (PROM) in order to simplify the control logic of the decoder devices.

According to a preferred embodiment of the invention, the first constant memory for comparison of the first and second interval length, as well as the second constant memory for comparison of the second and third interval length etc. comprise 8-bit memory positions or memory cells. Eight comparison tables can then be placed in the constant memories with their respective expectation fields, the first table e.g. is formed by the first bit of the memory cells, the second table is formed by the second bit of the memory cells, etc. By means of selective addressing and selective readout of the currently used table, up to eight different contrast line patterns can optionally be recognized with one decoder connection, whereby the applicability of the device according to the invention is increased.

The binary video signal comprises, for example, when the scanning beam runs over a darkly colored area of the data field, a first amplitude, Hi, and it comprises a second amplitude, Lo, when the scanning beam runs over a bright, character-free area of the data field. The assignment of the amplitudes Hi and Lo is arbitrary, and the opposite assignment of the two amplitudes to light and dark areas of the data is also possible.

The intervals of the video signal whose length is determined preferably extend from a. rising edge to the next rising edge, as well as overlapping from the falling edge located between these rising edges to the next falling edge of the video signal. The third interval then extends from the second ladder flank to a subsequent ladder flank, etc. As the intervals extend from ladder flank to ladder flank or from trailing edge to trailing edge, it is ensured that blurred edges of the contrasting lines of the contrast line pattern - which usually with all contrast lines proceed like-mindedly and uniformly - essentially do not affect the interval lengths, so that the decoder device according to the invention also recognizes the contrast line pattern that is produced under different printing conditions .

To increase the recognition security, contrast line patterns can be used with a flawless start or precursor zone of predetermined length, the precursor being arranged in front of the first contrast line. The measurement of the interval lengths then preferably only starts when an error-free precursor zone with the predetermined length appears in the video signal.

The measurement of the interval lengths is preferably terminated when an arbitrary interval length exceeds a predetermined maximum value which is equal to the maximum interval length appearing in the contrast line pattern. Likewise, a continuous measurement of the interval lengths is preferably terminated when the ratio between two consecutive, measured interval lengths lies outside the predetermined value range. In both cases, the utilization is interrupted at the earliest possible time and the decoder device is again reset to its active state.

The ongoing measurement of the interval lengths is likewise preferably terminated when a character-free intermediate zone of a predetermined duration corresponding to the maximum scanning distance between the lines of the contrast line pattern is sensed. The decoder device is then reset to the active state and is then ready for carrying out a new* exploitation.

The contrast line pattern further preferably comprises a character-free trailing zone with a length such as e.g. corresponds to the length of the character-free precursor zone A contrast line pattern recognition signal is then preferably only emitted when the video signal also contains a character-free successor zone of the predetermined length.

In order to increase the redundancy of the recognition process and thereby reduce the error probability, the same line is preferably scanned n times, and a contrast line pattern recognition signal is first emitted when. a contrast line pattern is recognized n times in succession.

The length of the mutually overlapping intervals of the video signal is preferably measured digitally and for this purpose counted in the counting circuit. The counter circuit comprises a timing control circuit which produces gate pulses having the same length as the corresponding intervals of the video signal. In order to measure the length of a respective interval of the video signal, a respective counter is arranged to which the gate pulses for the relevant interval are supplied to a gate input. The counters' counting inputs are connected together with a clock or pulse generator, which emits clock pulses to the counters during the occurring gate pulses. The final position of the individual counters then corresponds to the respective length of time. of the respective gate pulses and thus to the corresponding intervals. Continuously counted interval count values address the corresponding constant memory, after the later interval count value has been counted, whereby the count can persist also for further interval count values.

The invention shall be described in more detail below

in connection with design examples with reference to the drawings, where fig. 1 shows a first arrangement of a contrast line pattern within a data field with data tracks, fig. 2 shows a second arrangement of a contrast line pattern within a data field, fig. 3 shows a third arrangement of a contrast line pattern within a data field, fig. 4 shows a light-dark distribution for different contrast line patterns perpendicular to the contrast lines, fig. 5 shows a section of the video signal as a function of time, the section corresponding to the contrast line pattern according to fig. 4a, fig. 6 shows a block connection core of the decoder device's counting circuit, fig. 7. shows a block diagram of the decoder device comparison table,

fig. 8 shows a further embodiment of the decoder device's comparison table, fig. 9 shows a block connection core of the decoder device's utilization circuit, fig. 10 shows a schematic representation of the structure of the comparison table, fig. 11 shows a pulse plot for the pulses produced in the timing control circuit of the counting circuit, and fig. 12 shows a pulse plan for the pulses processed within the selection circuit.

In fig. 1 - 3 different identifications 50 are produced, e.g. adhesive price labels, such as is attached to a container, a package or one or another item of goods and appears in any position and alignment on a picture window. The image window is determined e.g. by means of the optical opening or aperture of a light point scanning device, e.g. a Vidikon tube, with the help of which the picture window is scanned first linearly, and then in a linear scanning grid.

Each of the identifications 50 has a data field which in at least one data track 51 contains contrasting characters 52 for identification of the item that is provided with this identification. The contrasting characters preferably consist of clear characters in one of the known, machine-readable fonts, e.g. in OCR-A font or OCR-B font. In a predetermined position and orientation in relation to the data track, a contrast line pattern 54 - also called position identification code PIC - is arranged, which comprises several parallel contrast lines with different distances and/or line widths. The contrast line pattern is according to fig. 1 placed in front of the data track, according to fig. 2 under the data track and according to fig. 3 at the end of the data track. The contrast line pattern 54 is perpendicular to the contrast lines designed asymmetrically to characterize the data field with regard to the beginning and end of the data tracks. Those in fig. 1 and 2 shown contrast line patterns, which are hereinafter referred to as PIC patterns, comprise a sign-free precursor zone

56 and a character-free successor zone 58.

Although only PIC patterns with three lines have been shown, PIC patterns with more than three lines can also be used. Furthermore, the PIC patterns - unlike fig. 1 - 3 - are also placed in a different position and orientation with respect to the data tracks, and furthermore two or more PIC patterns can also be placed on an identification field 50.

As shown in fig. 1, the image window becomes, respectively one for the image window corresponding image, e.g. on a Vidikon tube impact plate, scanned step by step with a step angle a from at least one scan line 60. It is essential that the PIC pattern before the reading of the data traces is first recognized in a safe manner and its position and orientation in relation to the scan beam 60 determined, as the data contained in the data trace characters can then be read using a subsequent raster scan in the direction of the data track. Fig. 4 shows the light-dark distribution perpendicular to the line direction for different PIC patterns which contain three lines and which are all asymmetrically structured and can therefore be used in accordance with the invention. Fig. 5 shows a section of the video signal which, when scanning a PIC pattern according to fig. 4a is produced as an electrical, binary signal, with dark areas of the PIC pattern being assigned to the amplitude Hi and bright areas of the PIC pattern being assigned to the amplitude Lo. Any light-dark fluctuations within the individual lines and distances of the PIC pattern are eliminated immediately after the scan in the electrical signal. Within the video signal section according to fig. 5, a character-free precursor zone corresponding to the zone 56 in fig. 1, a first interval Tl from the first rising flank to the second rising flank, a second interval T2 from the first falling flank to the second falling flank, a third interval T3 from the second rising flank to the third rising flank and a fourth interval T4 from the second falling flank to the third fall flank, and. moreover, a trailing zone corresponding to the zone 58 in fig. 1.

The decoding of the PIC pattern, e.g. according to fig. 5, takes place in accordance with the delta-distance method, whereby successive and mutually overlapping intervals are tested, i.e. Tl, T2 and T2, T3 and T3, T4 are in a predetermined relationship to each other given by the PIC pattern to be decoded. If the value of the quotients between successive, mutually overlapping interval lengths lies within predetermined value ranges, whereby the range widths are given by the print blurs and digitization blurs, the sought-after PIC pattern is very likely present.

Fig. 6 shows the counting circuit which forms the input to the decoder device according to the invention and which counts the interval lengths T1 to T4 and makes these available as binary values for further processing. The counting circuit contains a timing control circuit 2 to which the video signal VIDEO is supplied and which on a first output emits a first gate signal Tl from a first rising edge to a second rising edge of the video signal, on a second output emits a second gate signal T2 from a falling edge following the first rising edge to a second falling edge of the video signal, on a third output emits a third gate signal T3 from the second rising edge to the next, third rising edge, and on a fourth output a fourth gate signal indicates T4 from the second falling edge to a next, third falling edge, cf. the pulse plane according to fig. 11. The gate signals Tl to T4 are individually fed to a gate input Gl - G4 to a respective counter 6, 8, 10, 12. Each counter 6-12 receives at its counter input CTl - CT4 clock pulses from a clock or pulse generator 14, which pulses are counted by the counters 6-12 as long as the gate signal Tl - T4 is supplied. The counter position that can be output on the counters' 6-12 outputs TC1 - TC4 then constitutes a measure for the length of the gate signals Tl - T4.

In the timing control circuit 2, a trigger signal E2 is generated from the falling edge of the gate signal T2, a trigger signal E3 is generated from the falling edge of the gate signal T3 and a trigger signal E4 is generated from the falling edge of the gate signal T4 and emitted on separate outputs. From the trigger signal E4, a signal PVENT whose length corresponds to to the character-free trailing zone after the end of the gate signal T4, and which is emitted at a separate output.

The counter circuit further contains a reset circuit 4 which receives the video signal VIDEO, and on a separate input receives an external reset signal RESET IN at the beginning of each scan line. The reset circuit 4 emits a reset signal RESET to the counters 6-12 reset connections RS1 - RS4. and to the timing control circuit 2 and to reset both the counters 6 - 12 and the timing control circuit 2 to the active output state when the video signal contains a character-free section - amplitude Lo - which is greater than the maximum scanning distance between the lines of the PIC pattern, this maximum scanning distance being given by the maximum distance within the PIC pattern multiplied by the maximum allowable scan angle.

The counter circuit further contains an overflow recognition circuit 40 which receives an overflow signal from the counters 6 - 12 overflow outputs OV1 - OV4 and then emits a reset signal OV RESET and then resets the decoder device to a new ready state.

Fig. 7 shows an embodiment of the decoder device's comparison table. The comparison table contains a constant memory (PROM) 28. The PROM unit 28 is organized so that the counter 6 counter position TC1 addresses separate lines in a first memory matrix, and that the counter 8 counter position TC2 addresses separate columns in the first memory matrix. The counter positions TC1 and TC2 are supplied to the PROM unit 28 via a gate connection 16, 18 by means of the trigger signal E2 after counting the counter position TC2. Within the first memory matrix, an expectation field is preset which comprises the memory cells in which the quotient between line address and column address lies within a predetermined value range. This value range corresponds to the quotient between the first interval length and the second interval length of the PIC pattern used. If a memory cell or memory position within the expectation field is addressed using counter positions TC1 and TC2, a comparison signal with a first amplitude is emitted, e.g. Hi, which signals that information corresponding to part of the PIC pattern used was searched for.

To similarly perform a comparison between the gate pulses T2 and T3, the counter position TC2 for the second counter 8 addresses the lines in a second memory matrix, and the counter position TC3 for the third counter 10 addresses the columns in the second memory matrix. The addressing takes place after the counter position TC3 has been counted and the counter positions T.C2 and TC3.with the help of the trigger signal E3 have been transmitted via the port connection 20, 22 to the PROM unit 28. Within the second memory matrix, an expectation field is also preset which includes the memory cells whose quotient between line address and slot address lies within a predetermined range which is equal to the value range for the quotient between the intervals of the PIC pattern corresponding to the gate signals T2 and T3. If a memory cell in the expectation field is addressed, a comparison signal with the first amplitude is emitted, e.g. the amplitude Hi. When addressing a memory cell outside the expected field, a comparison signal with a second amplitude Lo is emitted.

The comparison between the third counter's 10 counter position TC3 and the fourth counter's 12 counter position TC4 takes place in the same way when addressing lines and columns in a third memory matrix which also contains an expectation field, since when addressing a memory cell within the expectation field, a comparison signal is emitted with the first amplitude Hi. The addressing of the third memory matrix takes place after the fourth counter's 12 counter position TC4 has been counted and the trigger signal E4 transmits the counter positions TC3 and TC4 via the gate connection 24, 26 to the PROM unit 28. The gate connections 16 - 26 consist of AND gates. The readout of the comparison signals LPIC1, LPIC2 and LPIC3 takes place by means of the readout signals EL2, EL3 and EL4 which are provided by delaying the trigger signals E2, E3 and E4 in a delay coupling 30, cf. the pulse plan according to fig. 12. The reading may only take place after the addressing of the first, second and third memory matrix has been adjusted.

Alternative to the embodiment according to fig. 7, the first memory matrix can be realized using a first constant memory, PROM1, the second memory matrix can be realized using a second constant memory, PROM2, and the third memory matrix can be realized using a third constant memory, PROM3, as it then advantageously can be used. three separate permanent memories with significantly less memory capacity.

The constant memory 28 comprises memory cells or memory positions, each of which has a size of n bits. As only one bit of the memory cells registered by the expectation field is seized for presetting an expectation field, up to eight different expectation fields for eight different PIC patterns can be placed in the PROM at the same time, as e.g. in PR0M1 the first expectation field is placed in the respective first bit of the memory cells, the second expectation field is placed in the respective second bit of the memory cells, etc. The same applies to PR0M2 and PR0M3. For a particular PIC pattern, the line and column addressing must then take place selectively in the corresponding bits of the memory cells. Furthermore, a switch 3 2 is connected after the PROM unit 28 which selectively reads out the comparison signals LPIC 1, .LPIC . 2 and LPIC 3 from the respective bits of the memory cells, and on its output it emits the utilization signal MUX PIC formed from the sequential comparison signals LPIC 1, LPIC 2<p>g LPIC 3 to the utilization coupling.

The decoder device's utilization circuit is shown in fig. 9. A buffer 34 receives the utilization signal MUX PIC and stores the comparison signal LPIC 1 - which indicates that the value TC1/TC2 lies within a predetermined range - as well as the comparison signals LPIC.2 and LPIC 3. The reading takes place by means of an input of the readout signals EL2, EL3 and EL4 which essentially acts simultaneously with the comparison signals LPIC 1, LPIC 2 and LPIC 3, cf. the pulse plan according to fig. 12. After all comparison signals are stored in the buffer as storage signals LPIC 1', LPIC 2', LPIC 3', these storage signals are output to an AND gate 36 which outputs an output signal LPIC when all 'storage signals LPIC 1' etc. have a first amplitude corresponding to the first amplitude of the comparison signals LIPIC 1 etc., see fig. 12. The output signal LPIC is supplied to an output circuit 38 which receives the video signal VIDEO and from the control circuit 2 receives the waiting signal number PVENT. The output circuit 38 emits a recognition signal PIC OUT when the video signal VIDEO during the presence of the waiting signal PVENT remains at the amplitude Lo which characterizes a character-free substrate. In this way, it is ensured that the decoded line pattern is followed by a character-free trailing zone which is equal to the PlC pattern's trailing zone 58..

The output circuit 38 is reset by means of the external reset signal RESET IN and then outputs a reset signal RESET A to the intermediate memory 34 and likewise resets this for a renewed operating operation. The buffer is further reset to zero using the overflow reset signal OV RESET when a counter 6-12 signals an overflow (flood). Fig. 10 shows in schematic representation how the comparison table, e.g. The PROM unit's 1 partial comparison table for comparing the quotient TC1/TC2 is organized. The table is presented as a storage matrix and the table's lines or rows are consecutively denoted by binary addresses. The columns or columns of the table are likewise consecutively denoted by binary addresses, since according to a preferred embodiment of the decoder device according to the invention a 5-bit representation has been chosen. All memory cells or memory positions with a specific value of the quotient between line address and column address lie on a line, the so-called expectation line, around which the expectation field lies within, which all storage cells lie whose address quotients lie within a predetermined value range. The counter positions TC1 - TC4 are likewise output as 5-bit words. The counter position TC1 addresses the table's lines and the counter position TC2 addresses the table's columns.

Claims (3)

Procedure for the identification of objects that appear in an arbitrary position and orientation and at arbitrary times on a picture window, and on a surface facing the picture window shows an identification in the form of a data field which in at least one data track includes contrasting characters with at least one contrast line pattern that characterizes the position and orientation of the data track and has several parallel lines with different distances and/or line widths, as the picture window is scanned linearly and a binary video signal is produced that corresponds to the scanned contrast sequence , in that the image window in a first process step is scanned for so long under different angles that a contrast line pattern is recognized, and further the position and alignment of the data field in relation to the image window is determined in a second step, and a raster scan takes place in the direction of the data track and the characters contained in the data track are read and decoded in a third step, characterized in that the interval length of the overlapping light and dark intervals of the video signal is measured for recognition of the contrast line pattern (PIC), that successively measured interval lengths are compared with each other and a comparison signal with a first amplitude is produced when the two interval lengths being compared are in a predetermined relationship to each other which correspond to the contrast line pattern's corresponding distances, and that a recognition signal (PIC OUT) is emitted when a comparison signal with the first amplitude is produced at one of the contrast line pattern's predetermined number of consecutive comparison steps. 2. Method according to claim 1, charac- in that the comparison between successively measured interval durations is performed in pairs in a two-dimensional comparison ning table within which the different possible, discrete values of an interval length are assigned to different table lines, and the different possible, discrete values of the subsequently measured interval length are assigned to different table columns, and that an expectation field is preset and includes the table places on which the quotient between the two consecutively measured interval lengths compared with each other lie in a predetermined' value range, and that a comparison signal with first amplitude is produced when the interval lengths compared with each other correspond to a table position within the expected field. 3. Method according to claim 2, characterized in that the expectation field lies in an area of the table which is limited by a line and a column respectively with minimum and maximum interval length. 4. Method according to claim 2 or 3, characterized in that two and tp successively measured interval/lengths to be compared with each other are fed into a separate comparison table with a separate expectation field. 5. Method according to claim 4, characterized in that different expectation fields are arranged in some comparison tables for corresponding, successively measured interval lengths for different contrast line patterns. 6. Method according to one of claims 2-5, characterized in that successively measured interval durations are entered in pairs in the comparison tables after the most recently measured interval length has been measured. V. Method according to claim 1, characterized in that each of the intervals of the video signal is measured from a rising edge to the next rising edge and overlapping from the falling edge located between these rising edges to the next falling edge. 8. Method according to one of the preceding claims, characterized in that the contrast line pattern comprises a character-free precursor zone with a predetermined length, and that the measurement of the interval lengths only begins when a character-free precursor zone with the predetermined length is determined in the video signal. 9. Method, according to one of the preceding claims, characterized in that the measurement of the interval lengths ends when an interval length exceeds a predetermined maximum value which corresponds to the maximum interval length occurring in the contrast line pattern. 10. Method according to one of the preceding claims, characterized in that the ongoing measurement of the interval lengths is terminated and a new measurement is started when the ratio between two successively measured interval lengths lies outside the predetermined value range and a comparison signal is therefore produced with the other amplitude 11. Method according to one of the preceding claims, characterized in that the ongoing measurement of the interval lengths ends and a new measurement is started when a character-free intermediate zone with a predetermined duration corresponding to the maximum scanning distance between the lines of the contrast line pattern. 12. Method according to one of the preceding claims, characterized in that the contrast line pattern comprises a character-free trailing zone of predetermined length, and that a recognition signal (PIC OUT) is only emitted when the video signal contains a character-free trailing zone of the predetermined length. 13. Method according to one of the preceding claims, characterized in that the interval lengths are counted digitally as a multiple of a predetermined pulse period, and .is further processed as a binary signal. 14. Method according to one of the preceding claims, characterized in that the same line of the image field is scanned n times, and that the recognition signal (PIC OUT) is only emitted when a contrast line pattern is recognized n times in succession. 15. Device for identifying objects in accordance with the method according to one of claims 1-14, comprising an optoelectronic scanning device with a rotatable scanning grid which outputs a binary video signal that corresponds to a linearly scanned image field and contains in binary form the contrast pattern of the scanned line, decoder devices for recognizing a scanned contrast line pattern (PIC) which characterizes the position and the orientation of at least one data track of a data field and contains several parallel lines with different distances and/or line widths, and devices for aligning the scan grid parallel to the data track and for reading the scanned characters of the data track, characterized in that the decoder devices (2-40) contain a counting circuit (2, 6 - 14) which receives the video signal and which counts the interval lengths of successively overlapping intervals of the video signal, that the decoder devices (2 - 40) contain at least one comparison table (28) which over a gate circuit (16 - 26) receives consecutively counted interval lengths ( TC1, TC2; TC2, TC3: TC3 , TC4; .'. ..) and emits a comparison signal (LPIC1, LPIC2, LPIC3) with a first amplitude when the two. Interval lengths compared with each other are in a predetermined mutual relationship which corresponds to the relationship between the corresponding intervals of the contrast line pattern, and that a utilization coupling (34, 36, 38) is arranged which emits an identification signal (PIC-OUT) with a uninterrupted sequence of a predetermined number of comparison signals with the first amplitude. 16. Device according to claim 15, characterized in that the counting circuit (2, 6 - 14) contains a timing control circuit (2) which generates gate pulses (Tl, T2, T3, T4...) which correspond to mutually overlapping intervals of the video signal whose pulse length is determined by successive rising edges or successive falling edges of the video signal, that the gate pulses. (Tl, T2, T3, T4 ....) are supplied to the gate input of a respective counter (6 - 12), and that the counters (6 - 12) on the counter input are connected together with a pulse generator (14) and counter the gate pulses and adds these as digitally counted interval lengths to the comparison table (28). 17. Device according to claim 16, characterized in that the counter circuit (2, 6 - 14) contains an overflow recognition circuit (40) which, in the event of an overflow of a counter (6 - 12), resets the decoder devices (2 - 40). 18. Device according to one of claims 15 - 17, characterized in that the comparison table (28) is designed as a two-dimensional constant memory (PROM), that the different possible, discrete count values of a first interval length address unambiguously assigned lines of the constant memory, that the different possible, discrete count values of the successively selected interval length address unambiguously assigned columns of the constant memory, and that there is a pre-set expectation field that includes the memory cells in which the quotient between line address and column address lies in a predetermined value range, and that when addressing a memory cell within the expectation field a comparison signal with a first amplitude is emitted, while when addressing a memory cell outside the expectation field a comparison signal with a second amplitude is emitted. 19. Device according to claim 18, characterized in that a separate constant memory (PROM 1, PROM 2, PROM 3...) is arranged for two consecutive interval count values (TC1, TC2; TC2, TC3; TC3, TC4). .) with its own expectation field. 20. Device according to claim 19, characterized in that successively counted interval count values (TC1, TC2; TC2, TC3; TC3, TC4 ....) address the assigned constant memory (PROM 1, PROM 2, PROM 3, ....) in pairs when the latest interval counter value has been counted and the time control circuit (2) emits a trigger signal (E2, E3, E4) for activation of the gate connection located in front of the constant memory (16, 18; 20, 22; 24, 26; ...). 21. Device according to one of claims 18-20, characterized in that each permanent memory (PROM) contains selectively addressable expectation fields and. different contrast line patterns, and that the comparison signals assigned to the different expectation fields can be selectively supplied to the utilization coupling (34, 36, 38) by means of a switched-on switch (32). 22. Device according to one of the claims 15-21, characterized in that the utilization coupling (3 4, 36 , 38) contains a buffer (34) which stores the comparison signals (LPIC 2, LPIC 3) until the appearance of the last comparison signal and then supplies all comparison signals to separate inputs to an AND gate (36), and that the AND gate (36) emits an output signal (LPIC) when all comparison signals are present with the first amplitude. 2.3. Device according to claim 22., charac- characterized by the fact that an output circuit (38) is connected after the AND gate (36) which receives the video signal and from the time control circuit (2) receives a waiting signal (PVENT) and which emits the recognition signal (PIC-OUT) when the video signal is waiting -, the presence of the signal contains a character-free trailing section. 24. Device according to one of claims 15 - 23, character, characterized in that a reset circuit (4) is arranged which receives the video signal and at the beginning of each scanning line receives an external reset signal (RESET IN), that the reset circuit (4) emits a reset signal (RESET) when the video signal contains a character-free section that is larger than the maximum scanning distance between the lines of the contrast line pattern, that the reset circuit (4) emits a reset signal (RESET) when the external reset signal (RESET IN) is present, and that the reset signal (RESET ) can be supplied to the counters (6 - 12) and to the timer limit (2) for zero setting.