DE2264517C3 - Device for reading binary information visually recorded on an information carrier - Google Patents

Description

The invention relates to a device for reading visually recorded information on an information carrier Binary information according to the preamble of claim 1.

A device of this type is known from DE-OS 50 146. In the known device are the information data is encoded in a 2-out-of-5 code. Each form 5 bits of the scanned data information hence a place and can be interpreted as a bit group. Checking whether a correct bit group was scanned, extends in the known device to check whether five scanned Bit contains two bits with the binary value L. If so, it is the five sampled Bit by a 2-out-of-5 code, which is therefore considered to be correctly scanned. This known way of testing the The sampled data information is only available in the case of special encodings (n-out-of-m code) and only then possible if all of the binary combinations possible in this code actually contain data assigned. For example, if with a 2-out-of-5 code only five of the ten possible binary combinations are actually assigned to a data content, then receives the test result of the known device no statement as to whether the scanned bit group is actually one of these five combinations used, and does not belong to one of the unused combinations. The known device is also open leave what happens if the test result shows that the sampled bit group is wrong.

The object of the invention is to design a device of the type mentioned so that a Validation of the individual data bit groups regardless of the type of code used can be carried out and that in the event of an incorrect data bit group, a new scanning process is carried out automatically is performed.

According to the invention, this object is achieved by the features in the characterizing part of the patent Proverb 1 solved. An advantageous development of the Invention is contained in the dependent claim.

With the present invention, a device is provided, the interfering signals, such as signals that as Response to foreign markings on an article or label are generated by information signals distinguished that read from the label

Become Vi . The device also contains circuitry which ensures that the signals read from the label are correct and that they have been read by a portion of the label which contains all of the information necessary to correctly identify the article. If, for example, there is no bit grouping corresponding to the preamble pattern, any bit grouping is incorrect, the counting of the bits leads to an incorrect result or, in the case of a porthole label, the optical scanner has not passed through the center of the label, the information read is rejected and the reading process repeated . This way you can get an incorrect result of the reading process and the related

far-reaching consequences can be prevented.

The scanner continues to scan the binary information on the information carrier as long as that bit signals obtained from the scan da * preamble identification pattern and the data bit groups correspond to known groupings. this could then no longer be the case if there is background interference on the information carrier are. In this case, there is the possibility of successfully reading the information carrier with the help an optical scanner in the part of the information carrier in which background disturbances are obtained Distort bit signals, in that the sampling in the same or in a different part of the information carrier is repeated.

A preferred embodiment of the invention is described in detail below with reference to the drawings described. It shows

F i g. 1 the scheme of an article identification device for reading coded labels,

Fig. 2 is a pictorial representation of a typical identification label as used in the facility of FIG F i g. 1 is used, and

F i g. 3 shows the block diagram of a circuit arrangement for reading the labels according to FIG. 2.

The in F i g. 1 includes label scanner station shown an article handling station, for example an output control counter 12 with movable Upper part 14 for transporting objects or articles 16 via a scanning slot 18 in the upper part 14 may contain. The upper part 14 can, for example, consist of two conveyor belts arranged next to one another 20 and 22, which form the slot 18, exist. Instead, as shown, the slot may be rigid in one Plate 15, which spans the space between the conveyor belts, may be provided. the Conveyor belts 20 and 22 transport the articles across the slot 18. The slot 18 can, for. B. approximately 6 mm wide and 15 cm deep, the depth of the slot being in the plane of the drawing in FIG. 1 is directed. For the sake of clarity, FIG. 1 the remaining parts of the upper part 14 and its Side rails not shown. The slot 18 is sized to ensure that an article 16 of an optical reading station arranged under the upper part 14 can be scanned.

The reading station 24 includes a light source 26, e.g. B. a laser or other light source that a Light bundle 28 emits in the visible or almost visible range of the spectrum, which is through a Focusing lens 30 is focused into a very fine scanning spot. The light beam 28 is from a Multi-surface mirror 32 is captured and directed onto the slot 18. The light source 26 can for example be a Be a helium-neon laser that is pumped so that it emits a continuous monochromatic laser beam Red light with a wavelength of approximately 6328 Å is generated.

The mirror 32 is driven about a shaft 38 by a motor 34 at a substantially constant speed rotated and is arranged rf. ic r the light beam 28 catches and directs through the slot 18 in the upper part 14. The mirror 32 can be offset with respect to the slot 18 be arranged so that dirt, etc. falling through the slot 18 does not impinge on the mirror 32. the Rotation of mirror 32 causes a series of light beam scans or projections through the Slot 18 each in a direction generally transverse to the direction of travel of the article 16. The number and sizes the surfaces of the mirror 32 are chosen so that there is always only one scanning spot on the underside of the Article 16 is generated.

On the underside or the bottom of each article 16 is a coded label 36, which is shown with reference to FIGS. 2 in The coded label 36 can, for example, be fastened by means of an adhesive 39 A label stuck on the article 16 or also ίο an imprint on the article 16. In the The description below assumes that the label 36 is an encoded paper label acts.

The reading station 24 also contains an optical filter 40 and a photosensitive recording device, for example a photomultiplier tube (photoelectron multiplier tube) 42, which are arranged one behind the other and offset from the slot 18. They are used to detect diffuse light reflected from the label 36

2i> or perceive. Diffuse instead of direct light was taken because direct light tends to make label 36 illegible. The optical filter 40 is the monochromatic light emitted by the light source 26 (if a monochromatic Light source is used) largely adapted and filters ambient light with wavelengths that are not are within the passband of the filter 40, out.

The photomultiplier tube 42 converts the diffuse light from the scanning of the article 16 The reading signal is converted into an electrical signal, the amplitude of which is the amount of light reflected from the label is equivalent to. An amplifier 44 connected downstream of the photomultiplier tube 42 amplifies this electrical output Signal, The amplifier 44 is connected to a consumer device 45, which is shown in FIG. 3 is coupled.

2a shows a machine-adjustable label 36 for item identification. Such a label is special suitable for use in supermarkets where the label is attached to the individual sales items or is printed on the sales item. The label can have encoded information about the price that Weight, the manufacturer code or a unique code number for the individual brand names, goods items and contain sizes or any combination of these indications. The label can be round in shape have to use the scanning device according to FIG. 1 to be able to put it without regard to the orientation "read" in a line, for example the dashed line 1-1. The label has an introductory or Preamble section 42 ', a data section 44' and a tail section 46 '.

The data portion 44 'may contain a number of digits which are in the form of rings of two different Reflectivity values are binary coded. For example, a black ring band can contain a binary "1" and a white ring band represents a binary "0". One can choose any two colors with significantly different ones Reflectance values for the optical

bo Use the scanner used to read the labels. The data section contains a number of ribbons, each of a given unit width, measured along any one Diameter, e.g. line 1-1. For example, 1.27 mm can be selected as the unit width of a band will. In this case, a black ring 50 with a width of 2.54 mm (i.e., two bands) represents two adjacent 1-bits. A white ring 52 with a width

1.27mm (i.e. one band) represents a single O-bit. The scanner scans the label with a point beam. The reflected light is perceived and converted into an electrical signal. Since the speed of movement of the point of light is known, the time between transitions is from black to white or from white to black a measure of the width of a white or a Black area as well as for the number of 1 or 0 bits, and it is used by the scanning device during the decoding process recovered.

The data section can be divided into groups of four contiguous bands, where each group embodies a decimal digit. There can be any number of these groups. For example, represents F i g. 2b shows a data section made up of five decimal digits in binary-coded decimal form, namely the number 64 626 The figure is shown with bars instead of rings for simplicity. The little dashes 54 and 56 mark the boundaries between adjacent bit positions or decimal digits. It is possible to have one to develop data grouping such that many adjacent bands are of one color. This would be no problem for the optical scanning device if the width of each data band is strictly adhered to and the label would always have a known fixed distance from the reading device.

In practice, however, neither of the above two conditions is met. The print is not perfect. Further the label may or may not be on a flat surface immediately above the slot 18 for example, be attached to the concave bottom of a spray can. So it has to be some Timing scheme must be built into the label. It has been found that this can be achieved in that the number of consecutive 1 or 0 bits (i.e. black or white bands) in a Decimal digit limited.

Table 1

Bit position

decimal number

0 12 3 4 5

Binardar
position

23 0 0 0 0 0 11111

22 0 0 1110 0 0 11

2i 110 0 10 110 0

20 0 10 10 10 10 1

Table 1 shows a code scheme in which none of the ten decimal digits more than two adjacent 1-bits or 0-bits are present. There are therefore in two adjacent decimal digits never have more than four adjacent bits of the same value. That that is, a transition from white to black or from black to white always occurs after no more than four Ribbons on. It has been found that a scanning device can be constructed that will work with all of the four adjacent bands of a given color, expected build tolerances works properly The device can be set up so that every time there is a transition from white to black or from Black to white takes place, reset or the phase is readjusted.

While any code that does not contain more than η consecutive 1 or 0 bits (n = 2 in the example given) can be used for the device according to FIG. 1, the code according to Table 1 is particularly suitable. It can easily be converted into a standard binary code by circuitry or with the help of a computer program by following the following two rules: If the 2 ³ bit is a 0, the standard binary value is obtained by subtracting the binary equivalent of the decimal number 2 from the value given in Table 1.

ίο If the 2 ³ bit is a 1, the binary equivalent of the decimal number 4 is to be subtracted.

From Fig. 2a it can be seen that the dal is preceded by a preamble section 42 'and followed by an end section 46'. The preamble section consists of a large number, for example at least five, adjacent bands of one reflectance value separated from the data by a band of the other reflectance value having a unit width (unit width). F i g. 2a shows an outer black ring and an adjacent inner white ring; however, one can just as easily choose the opposite colors. An outer ring at least five units wide is provided so that the optical scanner does not mistake it for data having more than four adjacent units of the same reflectivity value. Since the inner band, which is a single unit wide, has the opposite reflectivity value than the outer band, it ensures that a transition occurs and therefore the optical scanner clock is reset so that it starts timing when the next one is scanned Data sets in.
The end portion 46 'in FIG. 2a consists (following the last data band) of a white band, a black band, a white band and a center 58 of at least seven black bands to the center. The center 58 must have a sufficient number of width units (unit widths) in order to

ensure that the scanning point runs through the center,

while the container and the label attached to it

pass the scanning device in the direction transverse to the scanning direction. It was found that

6 7 8 9 a center of at least seven bands for the

45 Scanning device is appropriate That the inner one

Center of the opposite reflectivity value surrounding band with the width of a single Unit ensures that a transition occurs when the sample point is from the data to the center or from the Center passes over to the data.

The system shown in Fig.3 unierzugi that of Label 36 (Fig. 2) read a series of validity checks to ensure that a Label and not the background on the article to which the label is attached is read and that the The system also includes a tracing trace through or nearly through the center of the label Clock circuit which is synchronized by the data read from the label 36.

In Fig. 3 is the output of the optical scanner 10 (with the device of FIG. 1 up to and including the Amplifier 44) connected to the inputs of two transition detectors 60 and 62. The amplifier 44 (Fig. 1) in the scanner 10 can when scanning a

Label 36 through the light beam 28 a signal of z. B. the shape of the signal 64. That means he can when the light beam 28 detects a black ring, a relatively high voltage, denoted arbitrarily

as a binary "1", and when the light beam 28 detects a white ring, generate a relatively low voltage, arbitrarily designated as a binary "0". The transition detector 60, which can be designed in any conventional manner, generates a brief pulse whenever a transition from white to black occurs. The similarly constructed transition detector 62 always generates a brief pulse when a transition from black to white occurs. The output signals of the transition detectors 60 and 62 reach the set input (S) and reset input (R) of a first flip-flop 66. The transition detectors are also connected to an OR gate 68, which always generates a pulse when a transition from black to white or occurs from white to black.

The 1 output of flip-flop 66 is at the data input of a reversible shift register 70 connected. This shift register is designed in a conventional manner so that upon receipt of a Shift pulse the data in it depending on the value of a control signal supplied at that point in time moved either to the left or to the right. The shift register 70 must have a sufficient Have capacity to hold the entire data section read from the label 36 as well as certain bits of information to be included in the preamble and in the end of the data.

The first different bit positions in shift register 70 are with certain AND gates and others Elements wired to validate groups of information bits. For example the first six bit positions of the shift register 70 are connected to an AND gate 78. The bit position 1 is connected to a blocking input of the AND gate 78. The other places are at normal inputs connected. The purpose of this AND gate is to also check the preamble of a label, which, as already mentioned, from at least five 1-bits (5 black bands) with a subsequent O-bit (White ribbon) exists.

The first four bit positions of the shift register 70 are connected to the inputs of a 4:16 encoder 80. This is a standard encoder that converts a 4-bit code into a 1-of-16 code (one of the sixteen outputs high, the remaining fifteen low) converts the ten outputs of encoder 80 to the correspond to the ten permissible of the sixteen possible four bit combinations according to Table 1 connected to the ten inputs of an OR gate 82. The OR gate 82 is at one Blocking input of an AND gate 84 connected.

The first four bit positions of the shift register 70 are also connected to a switching mechanism 86, which is activated when the end portion 46 'including the first black band of the center 58, i.e. H. 0101, in the bit positions 4,3,2 or 1 of the shift register is present

The output of the OR gate 68 is connected to an input of a clock circuit 91, the two control signals for each bit of the sampled information, namely, "CLOCK" and "STROBE" generates the pulse "CLOCK" appears here in time by 100 ns relative to a black White (or white-black transition) delayed The »STROBE« impulse appears 150 ns after the »CLOCK« impulse.

The CLOCK signal arrives at the shift register 70, where it advances the bits in this shift register and at the S input of a counter 100, the count value of which is changed by 1 by each CLOCK signal.

The signal STROBE reaches that of the AND elements 78, 84 and an AND element in the switching mechanism 86.

The counter 100, to which the signal CLOCK is fed, is a conventional binary counter which, under the control of a corresponding control signal, counts either up or down. The counter is connected to two encoders 101 and 102 . The encoder 101

ίο always generates a pulse CT4n when the count value of the counter is an integer multiple of the decimal 4. The encoder 102 generates a signal CT24 whenever the count value of the counter is 24. This number is equal to the number of data bands (5 digits, 4 bands per digit) plus the first four bands of the end section 46 'of the label 36. A carry-out signal CO appears after the counter has reached the count value 0 and then receives another decrement pulse.

In the following description of the mode of operation of the circuit arrangement according to FIG the following is assumed: It is assumed that the individual switching elements or circuit stages Signals come in on the left or at the top and run out on the right or at the bottom. Exceptions are by "filing." marked. A relatively high-voltage signal, also called a "1", corresponds to the sampling of a Black band of the label 36, while a relatively low-voltage signal, also called a "0", the Scanning a white band of the label corresponds to An OR gate generates a high output signal (1), when one or more of its input signals are high. An AND gate generates a high output signal (1) when all of its inputs are high (1). A low signal on one with a small circle marked input of an AND gate or an OR gate means that this signal is within of the relevant OR or AND element acts as a high signal. Flip-flops are activated by high signals set and reset When a flip-flop is set, it generates a high and on at its 1 output its 0 output has a low signal.

When describing the mode of operation of the circuit arrangement according to FIG. 3 assumes that flip-flop 79 is initially reset and that counter 100 has a count value of zero. Then, when the optical scanner 10 scans an article 16 (Fig. 1), the amplifier 44 sends a sequence of alternating high-voltage and low-voltage signals, respectively

so the color changes when the article is scanned by the light beam 28. These color changes can result from the fact that the light beam over images, characters or text material on a container scans or scans a label 36. The transition detectors 60 and 62 therefore generate continuous, but aperiodic pulses, the changes from relatively dark to relatively light areas on the Container. A pulse from one or the other of these detectors activates the clock circuit 91.

The CLOCX pulse causes the data in the shift register 70 to be shifted to the right and a new information bit to be entered from the data flip-flop 66. This flip-flop is either set or reset, depending on which of the transition detectors 60 or 62 last generated a pulse. when the flip-flop 66 is set, it indicates that the scanner 10 is a black or relatively dark signal

is received, and when the flip-flop is reset, it indicates that a relatively bright or white signal is being received by the scanner 10.

The data is continuously monitored by the AND gate 78 as it enters the shift register 70. This AND element is scanned by the STROBE signal a short time (150 nanoseconds) after a CLOCK pulse has advanced data into the shift register 70. Whenever the first six bits in the shift register 70 contain data corresponding to five black bands and a subsequent white band (i.e. the shift register positions 2 to 6 contain ones and the shift register position 1 contain a zero), it is assumed that the scanner has passed the preamble section 42 'of the Has touched label 36. When the delay element 98 then sends out the signal STROBE, the AND element 78 is activated and the flip-flop 79 is set.

When AND gate 78 is activated and consequently flip-flop 79 is set, this is an indication that the scanner may have scanned the preamble portion of a label. Further checks confirm or refute this assumption. When the flip-flop 79 is set, the low output signal at its 0 output causes the reset signal to be removed from the counter 100 so that the counter can advance when the individual successive CLOC / C signals arrive at its 5 input. Assuming that the scanner is actually scanning a label, the data bits following the preamble section are inputted into shift register 70 bit by bit under the control of the individual CLOC / C pulses. During this sampling, the clock circuit 91 is periodically resynchronized by transitions in the data which, due to the correct selection of data bit groupings in the manner already explained, need not occur after more than four CLOCX pulses. When the counter reaches the count value 4, which indicates that the first four data bits have been received, the AND gate 84 is scanned by the S77? OSE signal. If the first four positions of the shift register contain one of the ten valid bit combinations according to Table 1, the output of the OR gate 82 is high so that the AND gate 84 is disabled. If any of the other 4-bit combinations are present in this shift register, as is likely when the scanning beam scans the substrate instead of a label or an area of the label sufficiently far from the center of the label, the output of OR gate 82 is low and the AND gate 84 is activated. When the AND gate 84 is activated, the resulting high output signal of the OR gate 122 resets the flip-flop 79 and thereby resets the counter 100. Whenever the flip-flop 79 is reset, a bit combination which is assumed to be represents the preamble section, the AND gate 78 is activated again, so that the flip-flop 79 is then set.

When the counter 100 reaches the count 8, ie 4x2, the AND element 84 is scanned again. As already explained, if the first four bit positions of the shift register 70 contain a valid bit combination according to Table 1, the AND element 84 is blocked the AND gate is activated and the flip-flop 79 is reset. This process continues until the counter reaches the count value 24.
Count 24 is important for three reasons.

First, any count other than 0 indicates that the preamble was perceived; Secondly it indicates that five groups of four data bits each have been read and determined as valid 4-bit combinations have been; and third, it indicates that the first four

ίο Bit positions of the shift register 70 should contain signals which correspond to white, black, white, black, ie the first four bands of the end section 46 ′ of the label 36. If, when the “count value 24” signal (CT24) and the “STROBE” signal reach the switching unit 86, this combination is not present, the switching unit 86 generates an output signal.

In one of many possible embodiments, the switching mechanism 86 can have a first AND element with two normal inputs connected to bit positions 1 and 3 of the shift register 70 and two blocking inputs connected to bit positions 2 and 4 of the shift register 70, as well as a second AND element with two the signals STROBE and count value 24 applied to normal inputs and a blocking input connected to the output of the above-mentioned first AND element. In this or other possible arrangements of switching elements, the switching circuit 86 generates a high signal at its output when it receives any signal combination deviating from high, low, high, low from the bit positions at its inputs (a) signals STROBE and count value 24 and (b) 1, 2, 3 and 4 of shift register 70 receives a low signal otherwise. The resulting high signal from the switching mechanism 86 causes the flip-flop 79 to be reset via the OR gate 122 , whereby the counter 100 is reset to the count value 0, so that the entire process must begin again.

It has been found that when the circuit arrangement according to FIG. 3 does not match the one described above Switching mechanism 86 is equipped and consequently does not carry out the validity check explained last, certain when scanning along the line 2-2 (Fig. 2a) can result in data combinations, that all other validity checks described are positive even if one is incorrect Reading of the label is required. It follows that when the circuit arrangement includes the switching mechanism 86 and this switching mechanism is not activated during the scanning, a strong guarantee is given is that the scan is made over a label and through the center of that label

After a label has been scanned without errors, a reset signal is generated at OR gate 122 and a VALID READ signal (valid reading) is generated. This signal can be used in a number of ways. For example, it can be sent to a data processing system (not shown) which has the effect that the information in the slider

bo gister 70 is lifted out to the data processing system. Instead, it can also cause the Information from shift register 70 to another storage shift register for any suitable one Purpose is pushed.

For this purpose 2 sheets of drawings

Claims (2)

Patent claims: 1. Device for reading visually recorded on an information carrier ßinärinformationen, which may also be background interference and wherein the binary information contains a unique preamble identification pattern and a data section with a known number of bits, comprising an optical scanner for scanning the information carrier and .cum generating Bit signals, the values of which correspond to the value of the bits on the information carrier, an arrangement which, when signals are received from the scanner in a bit grouping which corresponds to the preamble identification pattern, generates a preamble signal which indicates that the scanner subsequently detects binary information on the information carrier Register, an arrangement which, on receipt of the preamble signal, causes data bits to be entered into the register, and a counter arrangement which counts the individual data bits as they are entered into the register and indicates when the known number of data bits is in the register is entered with the known number of data bits divided into groups each of which matches any of a number of known binary groupings and each scanned group is checked for that match, characterized in that the optical scanner repeats the test periodically for such a period , until the label (36) is recognized as error-free that an arrangement (80, 82, 84) is provided which responds to signals stored in register (70) as well as to a given count value (CTAn) in j5 of the counting arrangement (100 , 101) responds and generates a signal which indicates that any of the data bit groups does not correspond to any of the known groupings, and that an arrangement (122, 79) is provided which responds to this signal, resets the counting arrangement and a new test Label (36) initiates 2. Device according to claim 1, characterized in that the information on the information carrier in addition to the preamble identification pattern and the data section has an end section (46) that in addition to the arrangement (80, 82, 84) there is a switching mechanism (86) which is on the count value (CT24) which occurs in the counting arrangement (100,102) when the number of bits in the data section and in the end section is perceived, and the register (70) responds to incoming signals and a signal bin. "0" is generated if the grouping in the end section was correctly scanned or a signal was received. If this grouping was scanned incorrectly, "1" generates that the resettable counting arrangement is kept in an inactive state in the absence of the preamble signal and is put into its counting state when the preamble signal is recognized and counts the bits that are counted by the scanner during scanning of the data and the end portion of the information carrier generated signals are displayed, and that the arrangement (122, 79) for resetting the counting arrangement and initiating a renewed examination of the label are also from the signal. "1" is controlled from the switching mechanism (86).