MXPA97004314A - Opto-electronic label with inte time base - Google Patents

Abstract

The invention relates to a reading label, ie read / write comprising a non-volatile memory with its control circuit, a load control circuit of an intermediate capacitor and a sequence generator that allows, on the one hand, send out sequences of optical signals in relation to the states of the different circuits and, on the other hand, analyze the optical signals that come from the exteri

Description

OPTO-ELECTRONIC LABEL WITH INTERNAL TIME BASE FIELD OF THE INVENTION With the current means it is possible to obtain autonomous opto-electronic labels that comprise a non-volatile memory and that can be fed, read or read and written remotely.

BACKGROUND OF THE INVENTION Swiss patent application No. 02 120 / 94-0 of 04/07/94 describes a label of this type that concentrates more particularly on the opto-electronic means for effecting the feeding of the label remotely, as well as for sending and receiving information by optical signals. It is evident that, independently of the opto-electronic part proper, the procedures that handle the communications between the label and the external reading / writing means constitute the most important part and condition the feasibility of this type of labels.

OBJECTS OF THE INVENTION The object of the present invention is to propose an opto-electronic label comprising simple and effective means of handling this communication. The opto-electronic label comprises at least one electronic memory capable of retaining its status in the absence of a power source, a control circuit of this memory, and a combination of electro-optical means provided with means for feeding the label and for transmitting light signals to the outside, characterized in that it comprises a time base that governs a sequence generator linked, at least indirectly, to constituent sub-assemblies of the label, the generator is provided with means for supplying light signals of characterized sequences that they allow to transmit to the outside the data that refer to said subeneambles. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 represents, by way of example, the schematic of the principle of a label according to the invention. Figure 2 represents, by way of example, the block diagram of a part of the constituent sub-assemblies of the label, according to the invention, more particularly the time base with the sequence generator, the power supply with its control circuit and a simple circuit for the analysis of light signals coming from outside. Figure 3 shows some characteristic voltages of the supply circuit and of the control means. Figure 4 shows some examples of sequences of light signals supplied by the sequence generator. Figure 5 represents, by way of example, a more detailed scheme of a sequence generator and memory demand circuit. Figure 6 represents, by way of example, a more sophisticated circuit of analysis of light signals coming from outside, coupled to the sequence generator. DESCRIPTION OF THE PREFERRED MODALITY Figure 1 shows 4 electro-optical cells 1, such as, for example, photovoltaic cells on amorphous silicon or AsGa cells on crystalline silicon. The selection of the cell type depends, of course, on the application in question. It is known, for example, that labels intended for industrial applications or access controls are in the form of a credit card, where the area available for electro-optical cells is relatively important, which allows the use of large-area cells but of reduced price, as in the economic electronic calculators. In addition, there are applications where maximum miniaturization is sought, where high performance cells with very little surface are needed. When a light beam is directed on these cells, the cells supply an electrical voltage that allows to feed the memory with its control circuit 2, by means of a diode 3 and an intermediate capacitor 4. This capacitor 4 plays an important role since allows to supply current points, which the cells will not be able to supply, and offers a reserve of energy so that, if necessary, an operation is finished if the luminous source of energy disappears. Preferably, the control circuit 2 will comprise a circuit that allows to limit this supply voltage in case of too violent lighting of the cells. A control circuit 2 is connected to the base of a transistor 5 which supplies, for example, 2 electrolucent diodes 6 by means of a resistor 7. It is also possible, by means of these electroluminescent diodes, to send outwardly luminous signals that they relate to the content of memory. These signals can be detected by known means. For example, if the diodes are of the IR type, an IR detector can be used, such as those used for the detection of people. It is also possible to send light signals by variation of the incident light, that is, by variation on the part of the light beam that is reflected by the label. In the simplest configuration where the memory is of a read-only type, it can be assumed that the control circuit 2 operates automatically when the supply voltage reaches a sufficient value, permanently analyzes the entire memory and sends the corresponding signals by means of the transistor 5, on the diodes 6. It is also possible to permanently read the contents of the memory as long as the cells 1 are sufficiently illuminated. However, this configuration does not offer great advantages in relation to a simple code bar. A more advantageous solution consists in using a read / write memory of the EEPROM type which conserves its data in the absence of a power supply. Therefore, it is necessary to be able to send the information that will be stored in the memory and order the different reading and writing sequences, from the outside. For this purpose, for example, the light beam directed on the label can be modulated. This modulation can be detected by an optical detector, for example a photodiode 8 connected by an input 9 of the control circuit 2 to an amplification and shaping circuit of the latter.

Another simpler solution consists of directly using all or part of the electro-optical cells 1 to detect these modulations. In fact, these cells can have a sufficiently slow reaction time to introduce control signals by means of short interruptions of light rays (total modulation or without modulation) to a sequence of the order of several KHz. These short interruptions are filtered by diode 3 and capacitor 4, in such a way that their influence on the supply voltage is negligible. The control signals generated by the cells 1 are then applied to the input 9 of the control circuit of the memory 2. Another possibility consists in using the electroluminescent diodes 6 as photodetectors. It is known that these elements, in certain configurations, can be reversible and, therefore, can be used as transmitters and receivers. It can be seen that it is possible to completely separate the energy input part represented by the cells 1, and the transmitter / receiver part of the information represented by the photodiode 8, the latter can be suppressed in certain cases, and the diodes 6. This separation it can also be done at the wavelength level of the luminous faces. For the part of energy supply is used, for example, a white light similar to sunlight. For the part of the transmitter-receiver, preference will be given to the infrared red, which gives a much more selective light and, therefore, more sensitive to external observations. In case where the diodes 6 are reversible and are also used as photodetectors, it is these that are connected to the input 9 of the control circuit 2. The three possibilities of branching of the input 9 are represented in dotted lines in Figure 1 In the last mentioned example, the energy contribution will therefore be made permanently, concentrating on the label a white light beam 10 and the communication of the information by a bidirectional infrared ray 11. The prism 12 of the figure allows to combine these two rays in order to represent schematically the functioning of the system, but it is evident that these two rays can come from two completely different sources and completely separated in space. There are many possibilities to generate these light rays and send them on the surface of the label, either directly, or indirectly, for example by means of a combination of optical elements, filters, lenses, optical fibers, etc. Figure 2 represents, by way of example, the block diagram of a part of constituent sub-assemblies of the label according to the invention, with more particularity, the time base with the sequence generator, the power supply with its control circuit and a simple circuit for the analysis of light signals coming from outside. The supply of the label is provided by the photovoltaic cells through the diode 20. The intermediate capacitor 21 allows to accumulate a certain reserve of energy capable of ensuring the functioning of the label, during a certain period of time, even in extreme cases in where the zener diode 22 limits the supply voltage to the top. The supply voltage branches off at the inputs of two comparators 23 and 24, through the resistor 25 and the zener diode 26 which fix a reference voltage Vz. The voltage divider formed by the resistors 27, 28 and 29 sets the voltages on the inputs + of these two comparators 23 and 24. In this case, it is a classical voltage comparison configuration. The output Cl of the comparator 23 will change to 1 when the supply voltage exceeds the value VI = Vz * (R27 + R28 + R29) / (R28 + R29), and the output C2 of the comparator 24 will change to 1 when the voltage of the power exceeds V2 = Vz * (R27 + R28 + R29) / (R29), as shown in the following figure .. These two comparators allow, therefore, controlling the supply voltage and in particular the load level of the capacitor 21. It is known that, in the programming of non-volatile memories, sufficient energy is needed to ensure the quality of the writing and guarantee the duration of the this. Therefore, it is preferred to forego this writing operation if the availability of this energy is not guaranteed, hence the importance of this power control. It is evident that it does not matter which circuit configuration capable of controlling those detection levels can be used. It is also possible to detect only one level or supplementary levels, according to the needs. The scheme of Figure 2 also comprises an internal time base 30 which can be a simple RC oscillator. This oscillator governs a sequence generator 31 formed of a combination of counters and logical circuits provided in order to generate the different sequences of the electro-optical signals that will be sent outwards. In another example, this generator supplies three SI, S2 and S3 sequences which will be described in greater detail in the following Figure. The SI frequency is connected to the input of an OR 32 logic circuit where the other two inputs are connected to the outputs of two AND 33 and 34 logic circuits. The AND 33 port inputs are connected to the S2 output of the generator and the output Cl of the comparator 23, while the inputs of the logic circuit AND 34 are connected to the output S3 of the generator and to the output C2 of the comparator 24. When the supply voltage is less than VI, the output Cl and C2 are at 0 and the logic circuits 33 and 34 are closed. Only the sequence of SI signals arrive at the output of the logic circuit 32. When the supply voltage passes between VI and V2, the output Cl passes to 1, which unlocks the logic circuit 33. The frequency S2 then passes over the second input of the logic circuit 32. The signal sequence at the output of this logic circuit is equal to S1 + S2. When the supply voltage exceeds V2, the output of C2 also passes to, which unlocks the logic circuit 34. The frequency S3 then passes over the third input of the logic circuit 32. The signal sequence at the output of that logic circuit 32 is then equal to S1 + S2 + S3. The signals at the output of the logic circuit 32 are applied to an input of the AND logic circuit 35. If they pass through the circuit, the signals appear at the output of this logic circuit, which is connected to the base of a transistor 36, connected to the light-emitting diodes 37 by means of the resistor 38. The light signals emitted by these diodes are, therefore, the image of the signal sequences at the output of the logic circuit 32, which depend directly on the states of output of the comparators 23 and 24 and, therefore, are representative among others, of the state of charge of the capacitor 21. These examples of configuration of these signal sequences are described in the following Figure. These configurations can be decoded by the optical reading means and it will also be possible to know, for example, if the light beam directed on the label has enough energy to feed the label and ensure the writing in the memory with sufficient security. Note that the frequency accuracy of the sequences of light signals sent to the outside depends directly on the accuracy of the time base 30. As long as it is lower, the external means of decoding signal frequencies and more delicate will be more complete, in need of frequency synthesizers and sophisticated treatment means. On the contrary, while the sequence of the signals is more precise, it will be easier to decode with a high noise level, which is particularly important when working at long distances.

A simple means to obtain this accuracy is to use a quartz resonator 38 as a reference of the time base. It is known that there are currently quartz resonators of three small dimensions that can be integrated even in small labels. We have already seen how the generator can generate the sequences of optical signals emitted to the outside. It is also possible to use it to analyze the signal coming from outside. In this simple example, the signals detected by photodiode 39 are amplified by the amplifier 40 which supplies at its output a signal on the input d of an 8-stage shift register 41, which receives a control signal on its clock input. which comes from the generator 31. The output of the fourth stage of the register is connected to the clock input of a jogger 42, whose input D is also connected to the power supply, while the output of the eighth stage of recording is connected to the reset inputs of this flip-flop 42. The output of the flip-flop 42 is connected to the second input of the AND logic circuit 35, when this output is 1 the logic circuit passes the signal sequences generated by the generator 31. If this output is 0 , the signals are cut. It is, therefore, a switch that allows to control the commissioning of the label from the outside. In fact, in the case where there are several labels in proximity to each other, there could be interference between them if they start their operation automatically at the appearance of a voltage on the photovoltaic cells. A rudimentary switch, like the one in Figure 2, can then be useful. As we will see in greater detail, the light signals coming from the outside are very short signals. The output of the amplifier 40 is therefore almost permanently at 0 and the shift register is at 0. If a signal of a longer duration is sent, the output of the amplifier 40 remains at 1 and this state 1 progresses towards the registration at rhythm given by the relatively low sequence command signals, over the clock input. At the end of the 4 clocks, the output Q4 passes to, which causes the output of the toggles 42 to 1 to swing and opens to the logic circuit 35. If the signal at the output of the amplifier 40 goes to 0, at that moment the jogger 42 it remains at 1 and the label supplies its light signals to the outside. To swing the jogger 42 to 0 and cut off the emission of the light signals, it is sufficient to send a signal with a longer duration, until the output S8 passes to l. At that time, the jogger 42 is brought to 0 and the logic circuit 35 is cut off. In this way, the time base and the sequence generator can be used to discriminate in a simple way the orders to start and finish the operation, which come from outside. Note that it is also possible to discriminate more or less long interruptions of light signals by inverting the output phase of the amplifier 40. This could be the case particularly if interruptions of the white light that feeds the photovoltaic cells are used to provide the orders Start and stop of operation. The input of the amplifier 40 will therefore branch directly on them, and not on the photodiode 39. In the following figures examples of analysis of the most sophisticated input signals are provided. Figure 3 shows certain characteristic voltages of the supply circuit and its control means. This mainly shows the switching of the outputs Cl to C2 as a function of the supply voltage and the detection levels from VI to V2. Figure 4 shows some examples of sequences of light signals supplied by the sequence generator. The sequence generator generates a first SI sequence in the form of fixed period and medium duration pulses, for example 4 microseconds for a period of 1 OOO microseconds. The sequence S2 is represented by a sequence of eight short pulses, for example 2 microseconds, which are repeated according to the same period as the SI sequence. This sequence of short pulses represents, in fact, an 8-bit logical information, in which it will be possible to distinguish 1 from 0 for the duration of the pulses. However, in the given case as an example, this distinction is made by varying the phase of the pulses within the period. Thus, if the position of these impulses is compared with respect to a reference signal, it can be considered that a total impulse in the first period from SI corresponds to bit 1, the impulse that falls in the second period to the bit 2, etc. The value of the bit is 0 and a corresponding pulse falls in the half-period where the reference signal is 0. Y is 1 if it falls in the half-period where the signal is 1. This 8-bit information may correspond to the content from a position in the same area or to the direction given by the control circuit of the same. Figure 5 provides an example of the circuit that allows generating these signals. Figure 4 gives the three possibilities of combining the light signals emitted by the label, according to the state of charge of the intermediate capacitor. When the signal is very weak, the signals corresponding to logical information are suppressed and only a minimum signal SI is maintained which indicates to the outside that the label is powered, although insufficiently to ensure its proper functioning. When the supply voltage is between VI and V2, the pulses corresponding to the logical information are added. It is also possible, for example, to read the label, but not write to it. For this, it will be necessary that the supply voltage is higher than V2. At that time, the signal S3 is added, which makes it possible to distinguish this condition by a double duration of the first impulse of the period of the sequence. Even when speaking of impulses of medium or long duration, it is always relative durations that allow to easily distinguish impulses from each other. However, these impulse durations are always weak in relation to the period of the sequence itself, in order to reduce consumption. In fact, if a current of 10mA is permanently injected into the LEDs, a very large area of photovoltaic cells must be present. By having 8 pulses of 2 microseconds and 1 pulse of 8 microseconds per period of 1 OOO microseconds, this consumption is divided between the ratio 24/1 '000, that is approximately 0.24 mA. This form is not possible without the use of the intermediate capacitor that is able to momentarily provide these current points. It can be noted that all the signals emitted outwards are grouped in the first half-period of the sequence. In this way, the second half-period of this sequence can be reserved for the reception of the signals coming from outside. These signals can be short pulses distributed in phase, such as the signals emitted during the first half period, as shown in Figure 6. There is also a uniform system, both for the emission and for the reception of signals. Figure 5 represents, by way of example, a more detailed example of a sequence generator and a memory control circuit according to the invention. This generator comprises a binary counter 50 comprising, in this example, 8 stages, and having the output Ql to Q8. The output Q8 has a period of 1 OOO microseconds, and Ql has a period of 8 microseconds, Q2 of 16 microseconds, Q3 of 32 microseconds, etc. The output Q8 is connected by the inverter 51 to the clock inputs of two flip-flops 52 and 53. The preset input of the flip-flop 52 is connected to the output Ql of the counter 50. This flip-flop is set to 1 at each start of the Q8 period., that is to say every 1 OOO microseconds, and then it becomes 0, in the middle period of posterior Ql, that is to say after 4 microseconds. The flip-flop 52 therefore generates pulses SI represented in Figure 4. The reset input of the flip-flop 53 is connected to the output Q2 of the counter 50. This flip-flop is weighted at 1 at each beginning of the period of Q8, ie each lOO microseconds, and then it becomes 0 in a period half of Q2 later, that is after 8 microseconds. The rocker 53 therefore generates pulses S3 shown in Figure 4. The output Q3 is connected to the clock input of a rocker 54, whose input D is connected to Q4. This jogger will therefore have the same period as Q4, that is 64 microseconds, but it will be out of phase in the middle period of Q3, that is 16 microseconds. The outputs Q and Qinv of the tilter 54 are derived by the capacitors 55 and 56 and the resistors 57 and 58, in order to form short pulses of the order of 1 to 2 microseconds displaced between them for a period of Q4, to be used. to generate the sequence S2. The label according to the invention also comprises an EEPROM 59 whose address inputs 60 are connected to a memory control circuit 61, connected to the counter 50, so that the change of direction is synchronized with the latter. The DATA outputs 62 of the memory 59 are linked to a demultiplexer 1/8 63. This demultiplexer has three selection inputs connected to the outputs Q5 to Q7 of the counter 50. The sequence of S2 is generated in the following manner. The pulses formed by the layers 55 and 56 are applied to an input of the logic circuits AND 64, respectively 65. The second input of the logic circuit 65 goes on the output of the demultiplexer 63. This output also goes on an inverter 66 whose output is connected to the second input of logic circuit 64. These two logic circuits 64 and 65 therefore work in alternation. When the first is blocked, the other is an intern, and vice versa. The outputs of these two logic circuits 64 and 65 are connected to an OR logic circuit 67. In this way, if the output of the demultiplexer 63 is 1, then the pulse formed by the capacitor 55 is that which will pass to the logic circuit output. 6; if it is at 0, an impulse formed by the capacitor 56 is the one that will pass farther. A sequence of pulses is thus generated as represented by S2 in Figure 4. The time distribution of these pulse sequences is a direct relation of the data contained in the memory 59, the data that appear sequentially in the output of the demultiplexer 63, which are analyzed by means of the outputs Q5 to Q7 of the counter 50. Note that data referring to other parameters different from the content of the memory can be transmitted in the same way to the outside, for example the addresses given by the memory control circuit, or any other data that relates to the operation of the label. Finally, the output of the logic circuit 67 is connected to the input of an AND logic circuit 68, whose second input is connected to the output of the inverter 51. During the half-period where this output is 0, the logic circuit 68 is blocked and does not stop pass the signals to the outside. This half-period can then be used in particular to receive and analyze the signals that come from outside. These signals can be shaped in the same way and with the same distribution over time as the output signals, which allows using a similar circuit for the decoding of this signal. Figure 6 represents, by way of example, a more sophisticated circuit of analysis of light signals coming from outside, coupled to a sequence generator. This generator comprises the counter 70, which is the same as the counter 50 of the previous Figure. The counter has outputs Q4 to Q8. The outputs Q5 to Q7 are connected to the selection inputs of a multiplexer, whose input is connected to the output of an amplifier 72 of the signals coming from outside. These signals are presented in the form of short pulses that are to be directed, according to their phase, on the clock inputs 72 of 8 D inverters 73 whose inputs D are connected to the output Q4 of the counter 70. In this way the 8 D inverters will change to 0 or 1 depending on whether the pulse arrives over the clock input during the half-period where Q4 is 0 or is 1. This combination allows reconstitute an 8-bit parallel information to be recorded by a second group of inverters D, whose inputs D are connected to the outputs of 8 preferred inverters, and where the clock inputs are branched at the output of an inverter 75, whose input is connected to the output Q8 of the counter 70. In this way it is to reconstitute the information byte by byte according to the distribution of the input signals in time, the latter are synchronized on the internal sequence generator. The latter also serves to generate the output signal sequences as well as to analyze the input signals. It is evident that many different combinations can be made, but the description thereof would not show more elements necessary for the understanding of the invention.

Claims (12)

1. CLAIMS; An opto-electronic tag comprising: at least one electronic memory capable of maintaining its state in the absence of a power source, a control circuit for this memory, and a combination of electro-optical means provided with at least one way of feeding the label and transmitting light signals to the outside, characterized in that it comprises a time base that governs a sequence generator linked at least indirectly to constituent sub-assemblies of the label, this generator is provided at least in a manner to supply the light signals of characterized sequences that allow to transmit to the outside the information referring to these sub-assemblies.
2. 2. The label according to claim 1, characterized in that the time base uses a quartz resonator.
3. The label according to claim 1, characterized in that the sequence generator comprises means for varying the duration of the light signals of the sequence as a function of the information to be transmitted.
4. 4. The label according to claim 1, characterized in that the frequency generator is provided so as to generate constant period sequences.
5. 5. The label according to claims 1 to 4, characterized in that the sequence generator comprises means for varying the phase of the light signals of the sequence within the period, depending on the information to be transmitted.
6. The tag according to claim 1, characterized in that the sequence generator is at least indirectly bound to the memory, and is provided so as to generate characterized sequences that correspond, at least in part, to the content of the memory.
7. The tag according to claim 1, characterized in that the sequence generator is linked, at least indirectly, to a feed control circuit, and is provided in a manner to generate characterized sequences that correspond, at least in part, to different states of the control circuit that correspond, more particularly, to different load states of an intermediate capacitor of the supply circuit.
8. The tag according to claim 1, characterized in that the sequence generator is linked, at least indirectly, to the circuit of the memory controller, and is provided so as to generate characterized sequences that correspond, at least in part, to the states of said control circuit.
9. 9. The label according to claims 1 to 4, characterized in that the sequence generator is provided so as to lock, within the period of said sequences, areas reserved for the emission of signals to the outside and areas reserved for the reception of signals. signs that come from outside. The label according to claim 1, characterized in that the sequence generator is linked to a circuit for analyzing light signals coming from outside, arranged so as to be able to differentiate the light signals according to their distribution over time. The label according to claims 1 to 10, characterized in that an analysis circuit is connected to a switching circuit arranged in order to start or stop the transmission of light signals to the outside, in response to the characterized control signals that come from of the outside. The label according to claims 1, 9 and 10 characterized in that the circuit for analyzing the light signals coming from outside is arranged in order to restore a logical information, depending on the phase between said light signals coming from outside and the reference signals supplied by the sequence generator;