FR2860625A1 - OPTICAL IDENTIFICATION LABEL ADDRESSABLE BY A PLAYBACK UNIT - Google Patents

Abstract

The tag comprises a logic circuit (5) connected to at least one photovoltaic cell (8), to an optical transmitter (7) and to a memory (6) containing an identification code (ID). The photovoltaic cell (8) makes it possible to supply the tag and to receive coded optical signals (S3). The label is formed by a stack of layers arranged on a support (4) and comprising first (1), second (2) and third zones (3). The first zone (1) forms the memory (6) and the logic circuit (5). The second zone (2) forms the optical transmitter (7). The third zone (3) consists of the photovoltaic cell (8). The second zone (2) can comprise several diodes (7) emitting light of different colors and the coding of the information can thus be carried out by color modulation. The reading unit may include a light source enabling the label to be supplied by illumination of the photovoltaic cells (8). The reading unit may include a camera.

Description

Optical identification tag addressable by a reader unit

Technical field of the invention

  The invention relates to an identification tag that can be addressed by a reading unit, the tag comprising a logic circuit connected to coded optical signal reception means, optical transmission means, a memory containing an identification code. and power supply means comprising at least one photovoltaic cell.

  State of the Art Traditionally, remote-powered contactless identification tags operate by radiofrequency transmission (RFID). Currently, the technique used to transmit information from an RFID tag to a reading unit is based on the use of carrier waves (typically at 125kHz, 13.56MHz, 860MHz and 2.45GHz) and a modulation of amplitude or impedance with Manchester encoding. The protocols used implement a bidirectional link.

  Optical or infrared (IR) radiation identification systems have also been proposed and can, in principle, be used in any field where RFID-type identification is used, and in particular in the field of logistics, large distribution, home automation, distributed sensor networks, etc., with however the need for direct view between the labels and the associated reading unit.

  Labels using visible wavelengths or IR are generally realized using macro-components whose autonomy is provided by a battery.

  Document FR2701142 describes an identification system making it possible to retrieve labeled objects from a reading unit emitting an IR signal. A tag includes a light emitting diode and an IR sensor for communication between the reader unit and the tag. The tag comprises two power sources, including a battery and a photovoltaic cell for amplifying the signal from the IR sensor. The label is thus complex, relatively bulky and heavy.

  OBJECT OF THE INVENTION The object of the invention is to remedy these drawbacks and, in particular, to produce a simple and low-cost construction identification optical tag.

  According to the invention, this object is achieved by the fact that the label consists of a stack of layers arranged on a support and comprising first, second and third zones, the first zone forming the memory and the logic circuit, at least a second zone forming the optical transmission means and at least one photovoltaic cell constituting at least one third zone and simultaneously forming the means for receiving the coded optical signals and the supply means.

  According to a development of the invention, each second zone comprises three diodes emitting light of different colors and the logic circuit comprises means for selectively controlling the diodes, so as to code information by color modulation.

  According to another development of the invention, the second zone and the third zone are adjacent.

  According to another development of the invention, the second zone comprises at least one liquid crystal display element by absorption.

  According to another development of the invention, the tag comprises a plurality of second zones respectively associated with a plurality of third zones and arranged in a matrix.

  The invention also aims at an identification system comprising at least one label according to the invention and a reading unit comprising an optical receiver, an optical transmitter, a control circuit, a memory and a man-machine interface.

  According to a development of the invention, the optical transmitter of the reading unit comprises a power light source for supplying the label by illumination of the photovoltaic cells.

  According to another development of the invention, the tag comprising a plurality of second zones and a plurality of third zones, the optical receiver of the reading unit comprises a camera.

Brief description of the drawings

  Other advantages and features will emerge more clearly from the following description of particular embodiments of the invention given by way of non-limiting example and represented in the accompanying drawings, in which: FIG. 1 represents a particular embodiment a label according to the invention.

  FIG. 2 represents a particular embodiment of a reading unit of the identification system according to the invention.

  Figures 3 and 4 show two particular embodiments of a label according to the invention, comprising a plurality of second zones and a plurality of third respectively associated zones.

  FIG. 5 schematically illustrates a particular embodiment of a stack constituting the label according to the invention.

  Description of particular embodiments

  The optical identification tag represented in FIG. 1 consists of a stack of layers comprising a first zone 1, a second zone 2 and two third zones 3. The stack of layers is placed on a support 4. The first zone 1 forms a logic circuit 5 and a memory 6 (for example of the ROM, EEPROM ... type) containing an identification code ID and connected to the logic circuit 5. The second zone 2 forms three light-emitting diodes 7 connected to the logic circuit 5 and transmitting signals S1, possibly modulated. The third zones 3 consist of photovoltaic cells 8 connected to the logic circuit 5 to which they transmit electrical signals S2.

  The photovoltaic cells 8 simultaneously enable the supply of the label by light absorption L and the reception of coded optical signals S 3, carrying energy and / or information. Thus, the label can be powered by capturing ambient light if the ambient light is sufficient, or by receiving light emitted by a reading unit associated with the label. The logic circuit 5 manages the various functions of the tag.

  The integration of the power function and the signal reception function in the same element makes it possible to reduce the size of the tag with respect to the optical tags according to the prior art. Furthermore, the label according to the invention can be produced in a single manufacturing process, resulting in an all-integrated device of very fine thickness, for example using thin film techniques known from microelectronics. .

  The second zone may comprise a plurality of light-emitting diodes 7 emitting light of different and, preferably, complementary colors. The second zone may also include liquid crystal display elements (LCD: Iiquid crystal display).

  In a particular embodiment, the second zone 2 comprises three light-emitting diodes 7 emitting light of different colors, for example red, green and blue (RGB), and the logic circuit 5 comprises means for selectively controlling light emitting diodes 7 as shown in Figure 1. Thus, the information transmitted by the tag can be coded by color modulation. For example, the coding can be achieved by using linear combinations of the three RGB colors, each encoded in three bytes. Thus, information corresponding to 24 bits can be transmitted. If the information is larger than 24 bits, several sets of light emitting diodes 7 each corresponding to 24 bits can be combined. Moreover, the natural color of the emission surface is superimposed on the colors of the signals S1 emitted by the light-emitting diodes 7, for example by organic light-emitting diodes (OLEDs), or by the elements of the LCD type.

  If, for reasons of simplicity, each color (red, green, blue, etc.) is coded on only one bit, the information may, for example, be encoded by a sequence of successive signals S1. Each of the signals S1 may, for example, be coded by a superposition of several colors (red and green, blue and green, etc.) or by a single color (red, green, blue, etc.). Transmitting a superposition of all colors, i.e., white light, for a predetermined time can be used at the beginning and end of a message to calibrate system parameters , for example the maximum transmission power and a unit duration of the signals S1. Thus, the coding can also take into account the durations of the signals S1 and the intervals between the signals S1. Manchester encoding may also be used to synchronize the received data.

  Preferably, the second zone 2 and the third zones 3 constituted by the photovoltaic cells 8 are adjacent to the support 4 as represented in FIG. 1. Thus, a part of the diffuse components parasite of the light emitted by the second zone 2 is recovered. by the photovoltaic cells 8 of the third zones 3, which increases the energy autonomy of the label.

  An identification system according to the invention comprises at least one optical identification tag and an optical pickup unit. The tags of the identification system communicate with the reading unit by emission and reception of light. The reading unit represented in FIG. 2 comprises an optical receiver 9 constituted by a camera, an optical transmitter 10, a control circuit 11, a memory 12 (for example of the ROM type) and a man-machine interface 13, by example a keyboard or a touch screen. The control circuit 11 manages the various functions of the reading unit. In FIG. 2, the optical transmitter 10 is constituted by a plurality of light-emitting diodes. In the embodiment shown in FIG. 2, the optical transmitter 10 emits a light L which is sufficiently powerful to be able to supply the label with illumination of the photovoltaic cells 8.

  The optical receiver 9 of the reading unit may also consist of optical sensors, for example photodiodes, capable of receiving the optical signals S1, possibly modulated, from the tag.

  The communication between the label and the reading unit can be effected by light modulation, either by symbol coding or by coding by different colors. Thus, the tag receives, via the photovoltaic cells 8, coded optical signals S3 emitted by the optical transmitter 10 of the reading unit. In response, the photovoltaic cells transmit electrical signals S2 (FIG. 1) to the logic circuit 5. The interpretation of the electrical signals S2 can give rise to a reading or writing in the memory 6 of the tag. The tag can also respond to the reading unit by sending the signal S1, modulated via light-emitting diodes 7.

  In FIGS. 3 and 4, the label comprises a plurality of second zones 2 associated respectively with a plurality of third zones 3 and arranged in a matrix. In FIGS. 3 and 4, the second zones 2a, 2b, etc. are constituted by elements of the LCD or OLED type and respectively send signals S1a, S1b, etc. Thus, each second zone 2 corresponds to a clean transmission channel, which makes it possible to increase the bit rate of the transfer of information from the label to the reading unit. Each third zone 3a, 3b can also receive coded optical signals S3a, o S3b and thus corresponds to a clean transmission channel of information from the reading unit to the label.

  In FIG. 4, the second zones 2 emit signals S1 of different colors. Thus, information is transmitted by color modulation coding and through a plurality of channels, which corresponds to a sequence of color images, each third zone 3 corresponding to a pixel of the image.

  In the case where the label comprises a plurality of second zones and a plurality of third zones, as represented in FIGS. 3 and 4, the optical receiver 9 of the reading unit preferably comprises a camera making it possible to distinguish the different transmission channels, for example, by image processing.

  FIG. 5 illustrates a stack of thin layers disposed on a transparent support 4, for example made of glass, and comprising the first zone 1, the second zone 2 and a third zone 3. The first zone 1 is illustrated by a single transistor 14, of the thin film transistor (TFT) type, which may, for example, be made of poly-silicon. The second zone 2 comprises an organic light-emitting diode 15 consisting of several organic layers 16 (16a, 16b, 16c). The third zone 3 comprises a photovoltaic cell 8 constituted by a photovoltaic diode of the PIN type, comprising a first semiconductor layer 17 with N-type dopants, a second undoped semiconductor layer 18 and a third semiconductor layer 19 with P-type dopants. The semiconductor layers 17 to 19 may, for example, be made by growth and etching of hydrogenated amorphous silicon.

  In FIG. 5, the photovoltaic cell 8 and the OLED diode 15 are disposed on transparent conductive layers 20, for example constituted by a material comprising tin (Sn), indium (In) and oxygen (0) (ITO: indium tin oxide). Contacts 21 are respectively arranged on the photovoltaic cell 8 and on the OLED diode 15.

  The invention is not limited to the particular embodiments shown. In particular, the second zone 2 of the label may include any kind of optical radiation emitter.

Claims (10)

claims   1. Identification optical tag addressable by a reading unit, the tag comprising a logic circuit (5) connected to coded optical signal receiving means (S3), optical transmission means (7), a memory (6) containing an identification code (ID) and supply means comprising at least one photovoltaic cell (8), characterized in that it consists of a stack of layers arranged on a support (4) and having first (1), second (2) and third (3) zones, the first zone (1) forming the memory (6) and the logic circuit (5), at least one second zone (2) forming the means optical transmission device (7) and at least one photovoltaic cell (8) constituting at least one third zone (3) and simultaneously forming the means for receiving the coded optical signals and the power supply means.   2. Label according to claim 1, characterized in that the second zone (2) comprises at least one diode (7) emitting light.   3. Label according to claim 2, characterized in that the second zone (2) comprises a plurality of diodes (7) emitting light of different colors.   4. Label according to claim 1, characterized in that the second zone (2) comprises at least one liquid crystal display element by absorption.   5. Label according to claim 3, characterized in that each second zone (2) comprises three diodes (7) emitting light of different colors, the logic circuit (5) comprising means for selectively controlling the diodes (7), in order to encode information by color modulation.   6. Label according to any one of claims 1 to 5, characterized in that the second zone (2) and the third zone (3) are adjacent.   7. Label according to any one of claims 1 to 6, characterized in that it comprises a plurality of second zones (2) respectively associated with a plurality of third zones (3) and arranged in a matrix.   8. Identification system comprising at least one label according to any one of claims 1 to 7, characterized in that it comprises a reading unit comprising an optical receiver (9), an optical transmitter (10), a circuit control unit (11), a memory (12) and a man-machine interface (13).   9. Identification system according to claim 8, characterized in that the optical transmitter (10) of the reading unit comprises a power light source for supplying the label by illumination of the photovoltaic cells (8). ).   10. Identification system according to one of claims 8 and 9, characterized in that, the label comprising a plurality of second zones (2) and a plurality of third zones (3), the optical receiver (9) of the reading unit comprises a camera.