MXPA96000821A - Electronic label for reading / writing opt - Google Patents

Abstract

The present invention relates to an electronic tag typically comprising an EEPROM type memory device. The label comprises electro-optical cells allowing power supply of the label, when the light strikes the cells. Electro-optical components also allow to receive signals from optical commands and to transmit optical signals to the outside, these light signals are related to the content of the memory device.

Description

ELECTRONIC LABEL FOR READING / OPTICAL WRITING BACKGROUND OF THE INVENTION Currently, there are numerous electronic tags on the market, allowing memorization of information in relation to an object or a product. The simplest labels do not comprise anything except a memory dedicated to reading purposes (ROM) and have for example an identification number. More systems Í.Í) developed provide read / write memorized information. This reading / writing allows modifications of information memorized in functions of evolution of time of the product, allowing therefore to follow up. The simplest systems use memory static or read-only memory (ROM) energized by a long-life battery, for example a lithium battery. More sophisticated systems employ erasable and programmable memories or electrically erasable programmable read-only memories (EEPROM), which provide the advantage of maintaining the information without needing external power, allowing suppression of the battery. Access to information is possible by establishing one or more contacts as it is done for micro circuit cards. However, more and more systems can be read, written or read / written at a distance, without necessity by ß_. Contact. To do so, all contactless systems currently known employ a magnetic coupling, which uses at least one coil. This comprises several disadvantages. For example it is impossible to mount this label on a metallic object, which represents a magnetic short circuit, which affects the intended energy to the label. Furthermore, it is impossible to place a multitude of labels close to each other, due to the danger of interference. u Finally, this coil represents a relatively voluminous and sensitive component. COMPENDIUM OF THE INVENTION The present invention relates to an electronic tag for reading / writing without remote contact, without having the above disadvantages. The tag comprises at least one electronic memory device, capable of retaining its state in the absence of power supply. This tag further comprises a command circuit for instructing the memory device. The label is characterized by a combination of cells similar to electro-optical cells assed in this way, to supply the memory device and the command circuit with energy, when incident by light on a cell surface. The tag is further characterized by transmission means connected to the command circuit and transmitting light signals to the outside, these light signals are related to the content of the memory device. BRIEF DESCRIPTION OF THE DRAWINGS 5 Figure 1 shows an exemplified functional diagram of the label according to the invention. Figure 2 shows a more detailed exemplified functional diagram of the memory device and its command circuit. +0 Figure 3 shows an exemplary embodiment of a label according to the invention. Figure 4 shows an exemplified label according to the invention that is combined with a bar code. Figure 5 shows an exemplified label according to the invention that is combined with a cross filar "'for purposes of optical signaling DESCRIPTION OF THE PREFERRED MODALITIES According to Figure 1, four electro-optical cells 1 are illustrated, which are for example photovoltaic cells based on GaAs or amorphous silicon cells, with base in crystalline silicon, these cells provide an electrical voltage when they are struck by light, the voltage allows the memory device and the command circuit 2 to be supplied with power, a diode 3 and a capacitor 4 arranged between cells 1 and 2, allow the filtering of the supply voltage Preferably, the command circuit 2 comprises a limiting circuit, allowing the limitation of the supply voltage in the case of too violent cell lighting. command circuit 2 is connected to the base contact of a transistor 5. Transistor 5 supplies transmission means, for example two electro-luminance diodes 6. A resistor -:? 7 is arranged between the transistor 5 and the diodes 6. By means of the electro-luminance diodes 6, it is therefore possible to emit light signals to the outside. These light signals are related to the related information in the memory device and are detectable by means known detection. In the case, when the diodes 6 are infra-red diodes (IR), then an IR detector can be provided, these IR detectors are well known and commonly used for the detection of personnel. It is also possible to emit light signals when the light varies incident, which means varying the part of the incident light that is reflected from the label. According to a simpler mode, when the memory device is only a readable memory device, it is possible to activate the command circuit automatically, when the supply voltage reaches a sufficient potential. This activation command circuit constantly explores throughout the memory and sends the corresponding signals to the transistor 5 and from there to the diodes 6. As long as the cells 1 are illuminated sufficiently, it is therefore possible to read the contents of the transistor permanently. memory device. Unfortunately, the above embodiment provides no essential advantage compared to a simple bar code. A more permanent solution is to use a read / write memory device (EEPROM) that holds information stored in the absence of a power supply. In this way, it is necessary not only to send from the outside, the information to be stored to a memory device, but also to control from outside the different stages of the reading and writing process using command signals. External signals relate to information and command signals. One solution consists of a modulation of the incident light directed to the label. These modulations are detectable by detection means such as an optical detector which is a photo-diode 8. Modulations detected are processed in the signals by the photodiode 8, which are connected by a supply contact 9 of the command circuit 2 to the amplification circuit . The internal configuration of the command circuit is given in more detail in accordance with Figure 2. Another and easier solution is to use part or all of the electro-optical cells 1 for detection of these modulations. These cells can, in fact, have sufficiently slow reaction times to allow the introduction of information (and command signals) into the incident light beam. Therefore, short interruptions of light having a frequency in the order of some kHz can be provided, and represent modulations (light or dark). These short interruptions are filtered by diode 3 and capacitor 4, so that their influence on the supply voltage can be disregarded. Signals generated by the cells 1 are applied by the power contact 9 of the command circuit in the memory device 2. Another even more interesting solution is to use the electro-luminance diodes 6 as photodetectors. It is well known that these elements can be used in an inverted mode and therefore can be used as emitters and as receivers. This configuration allows a total separation in a part with respect to the power supply, represented by cell 1 and in a part with respect to the emission / reception of information (and of command signals), which are represented by diodes 6. This separation it can also be carried out at the level of the light wave range. With respect to the power supply, it is proposed to use a first light component, for example of white light similar to sunlight. With respect to the emission / reception of information, a second component of preferential infra-red light (IR) is employed, which results in a selective light band, which is less sensitive to external disturbances. Reversible diodes 6, also used as photo-detectors, are connected to the supply contact 9 of the command circuit 2. The three aforementioned possible interconnections of the supply contact 9, are indicated by the dotted lines according to Figure 1 5 According to the last example cited, the power supply occurs in a permanent way to the "" "" centering a beam of white light 10 on the label and the communication of information is performed by using a bidirectional IR beam 11. Prism 12 allows combining the two beams, which are presented in a schematic form according to the Figure 1. There are of course many other possibilities to generate these light beams, and for their transmission to the surface of a label. It is possible to send them in a direct or indirect way to the label, using for example an optical fiber. Figure 2 shows an exemplary internal configuration of the memory device and its command circuit. The command signals 20 are applied to the supply contact of a processing circuit 21. The latter generates the different sequences for the operation of the labels and supplies signals • ±? rectangular to a power contact of a serial / parallel converter 22. The information is transmitted from the outside in a serial way using beams of light. The converter is mounted in a way to decode the transmitted information. This information decoded allows a memory device command 23, comprising address feeds 24, data feeds / outputs 25, a read feed 26 and a write feed 27. The memory device (EEPROM) typically comprises a booster that increases voltage 28, which is activated during a write process to set newly recorded data. There are numerous known configurations of this type and for this reason, no further details will be given.

"'Figure 3 shows an exemplary embodiment of the label according to the invention. According to the Figure, different electronic elements are mounted on a support 31, fixed in a tubular enclosure 5. A first side of the support 31 comprises a capacitor 33 corresponding to a capacitor 4 according to Figure 1. A second side of the support 31 comprises four electro-optical cells 34, two electro-luminance diodes 35, an integrated circuit 36 comprising a l? command circuit and a memory device and a diode 3 according to Figure 1. According to a classical embodiment, the support 31 can be a printed circuit of both sides comprising interconnections between the different components. The capacitor 33, for example an SMD capacitor, is soldered directly to the printed circuit. The printed circuit 36 can be arranged with stops for fixing by thermocompression, while electro-optical elements are connected by connection 37. The above set is given as an example for a better understanding of the invention. With regard to micro-assembly methods, we are currently seeing rapid advances, allowing for example a meeting of a plurality of elements in one and the same substrate and therefore reduce the number of components and interconnections. In the future, remarkable simplifications can be expected in this domain. Next, the dimensions of this label will be discussed. Simple light sources, for example laser diodes, can emit a beam of light with a typical intensity in the order of magnitude of 100 W per cm2. Known electro-optical cells have an efficiency of 10%. Therefore, it is possible to obtain an electrical power of 0.1 mW per mm2 of cell surface. In order to write a byte in an EEPROM memory device, it is necessary to switch on a booster that increases voltage and provides a certain power. The electro-optical cells must provide a typical energy of 2.5 mW during 2.5 msec (Faselect). In order to transmit information to the outside, electro-luminance diodes typically have to be provided with at least 1 mA, allowing the latter to emit light signals that can be easily detected and represent an energy consumption of 5 mW at 5 volts. To generate the energy, it will be necessary to have a total cell surface of 50 mm2, resulting in a relatively large and expensive label. A simple method to avoid this disadvantage is to operate the label in time intervals. Light signals are written or sent only in very short periods of time. The filter capacitor is therefore discharged for very short periods of time and can be recharged later for longer periods of time, reducing the average power consumption. Write 1 byte for example 2.5 W for 2.5 msec. In order to reduce the average power consumption, the capacitor recharges for 7.5 msec, resulting in a total write time of 10 msec. The corresponding average energy consumption is related to 2.5 mW * 2.5 / (2.5 + 7.5) = 0.625 mW. The transmission of signals abroad consumes 5 mW. Since IR diodes can be modulated at high speed, allowing one byte to be sent within a few milliseconds, the average power consumption decrements of the high-modulated IR diodes are easily reduced to 10% of the peak value, that means 0.5 mW. The above-mentioned different cycle ratios can be generated directly by the command circuit according to Figure 1. Therefore, it is possible to reduce the total cell surface needed by a factor of 8 to 10, representing a cell surface for example of four cells with 2 mm2 of surface each one. The integrated circuit comprises a command circuit and the related diode typically requires a surface of 4 mm2 (techno Faselec SAC MOS 2 microns, 256/8 bits capacitor). As regards the electro-luminance diodes, they require a surface area smaller than 0.5 mm / 0.5 mm. For a write procedure, the capacitor produces a current 0.5 mA for 2.5 msec. In order to limit the voltage drop to an acceptable value, the capacity of the capacitor must be in the order of magnitude of some microFarads. It is proposed to use an SMD capacitor with a minimum size of 1812. The energy evaluations carried out previously correspond to the current state of the art and to components available in commerce at present. Therefore, it is expected to put EEPROM memory devices on the market, which consumes 10 times less energy for a writing procedure and therefore will reduce the dimensions of the labels. In the present case, the entire label is mounted in a tubular enclosure 32, having a diameter of 8 mm and a height of 4 mm (scale factor of 8) as illustrated by the embodiment according to Figure 3. The The enclosure is sealed on one side with a droplet of resin 38 and on the other hand by a transparent lens 39. The latter is fixed in a recess in the enclosure.

Figure 4 shows an exemplified label according to the invention combined with a bar code. In order to use the label according to the invention, a light beam has to be sent and the light signals will be received in response. Therefore there is a great analogy with the means necessary to read a barcode. The label 41 according to the invention can, without difficulty, be combined with a bar code 42. The latter represents a part of information not __u changeable, while the label according to the invention represents a part of exchangeable information. Figure 5 shows an exemplified tag according to the invention that is combined with a filar cross for purposes of optical signaling. Is good It is known that, recently, the means of image recognition progress rapidly. These means allow, for example, a high precision location for example. With respect to the present invention and in accordance with Figure 5, these image recognition means, associated with a filar cross 51, allow a placement of high precision to point at the cross filar. Therefore, it is possible to place a label 52 in the center of the cross-hair 51 and direct the light beam accurately to the label.

Of course there are numerous other possible combinations for producing a label according to the invention. A description of these labels however does not provide any new elements for the understanding of performance.

Claims (8)

1. CLAIMS 1. Electronic tag, characterized in that it comprises: at least one electronic memory device, capable of retaining its state in the absence of power supply, and a command circuit for instructing the memory device, with which the tag comprises the less a combination of cells such as electro-optic cells mounted in such a way as to supply a memory device and the command circuit with power, when incident by a light beam on a cell surface and transmission means connected to the circuit command and mounted in such a way as to transmit light signals to the outside, these light signals are related to the content of the memory device.
2. 2. Electronic tag according to claim 1, characterized in that the transmission means are electro-luminance diodes.
3. 3. Electronic tag according to claim 1 or 2, characterized in that the electronic tag comprises detection means for modulating the received light and processing means for processing signals out of the modulating light, these processing detection means are mounted in a manner such that they command the command circuit from the outside by means of the signals.
4. 4. Electronic tag according to claim 1 or 3, characterized in that a part or all of the electro-optical cells are used to detect the modulations.
5. 5. Electronic tag according to claim 1 or 3, characterized in that the electro-luminescence diodes are reversible diodes and are used as signal detectors. Electronic tag according to claim 1 or 3, characterized in that the light comprises two light components having different wave ranges, the first light component is used to supply power to electro-optical cells of the label and the second Light component is used for signal transmission. Electronic tag according to claim 1, characterized in that the electronic tag is placed in the vicinity of a bar code, allowing the bar code to be read with the light beam. 8. Electronic tag according to claim 1, characterized in that the electronic tag is placed inside a filar cross, the light beam is associated with means of detection and image recognition can be pointed or addressed to the electronic tag by recognition of the cross filar.