NL1001533C2 - Contactless electronically read identification card - Google Patents

Abstract

The circuit (4) on the card is powered by a photo-voltaic panel (1) which converts ambient light (9) to a voltage which is stored in a capacitor (3) via a diode (2). A direct connection (5) to the circuit can be used to detect signal-bearing variations in the ambient light. The code which identifies the card is fed (6) to a liquid crystal modulator (7). Incoming light (10) is reflected by a mirror (8) after passing through the modulator (7).

Description

-1-

PROXIMITY IDENTIFICATION SYSTEM, POSSIBLE WITH SENSORS, BASED ON MODULATED REFLECTION OF 5 OPTICAL SIGNALS

Contactless identification systems, in which the energy supply of an electronic identification label takes place by means of an interrogation signal, usually make use of an electromagnetic transmission field, with a frequency varying from approximately 100 kHz to approximately 13.5 MHz. An example of such an identification system is described in applicant's European patent application 92202927.7. The identification label usually consists of a contactless chip card with the standardized dimensions of a bank card or credit card. In order to achieve the lowest possible cost for the chip card in such systems, the chip card uses as few electronic components as possible, usually a chip and a coil. The coil is needed to convert the electromagnetic field into energy supply for the electronic circuit and to realize the communication between the transmitter / receiver and the chip card.

A still further reduction in the number of components, whereby further cost reduction is possible, has led to developments in which the coil necessary for the radio-frequency contactless transmission was also integrated on the chip. Hereby, due to the low quality factor of the coil and due to the extremely small dimensions, a very poor efficiency with regard to the energy transfer arises, and thereby a very small communication distance.

The object of the present invention is to overcome this problem and to make contactless contact. -2- identification system, in which the chip card has a relatively low cost price, by applying two or only one optoelectronic element in the form of an integrated circuit (chip), which is fitted in this card and whereby the energy supply, both if communication takes place optically. In addition to an identification code, information from sensors, such as, for example, a temperature sensor or, for example, biosensors, can of course also be transferred.

Since the power requirement of the electronic circuit must be minimized, the system according to the invention uses the passive modulated reflection of the optical transmitter signal for the return signal, instead of using an active optical component, such as for instance a light-emitting diode (LED). By making use of reflection, or even better retro-reflection, whereby the reflection takes place exclusively in the direction of the interrogation signal with the aid of a special retro-reflective mirror, the efficiency of the signal transmission and thus the distance that can be bridged without contact can be further increased. increases. The energy supply of the electronic circuit is effected by means of one or more photovoltaic element (s), preferably integrated on the chip. By modulating the transmission level of the optical transmitter, it is possible to transfer information from the transmitter to the card, so that the authenticity of the identification label, or of the 30 received, is received using known so-called "challenge" and "response" techniques. messages, can be fixed.

By making use of the so-called "free carrier absorption" effect in, inter alia, silicon, whereby depending on an applied potential through variation and recombination of "electron / hole" pairs, a variation in the optical absorption coefficient occurs, it is possible to voltage applied to a photosensitive silicon layer, to transfer information from the label to the 1 oo <e 3:> -3 optical transmitter / receiver. In this case, only one optical component is required to receive energy and data information from the optical transmitter / receiver and, for example, by varying the load causing the voltage to vary, using relaxation and recombination and the associated variation of the absorption coefficient, transfer information from the label to the optical transmitter / receiver.

In case using variable absorption and reflection via the "free carrier absorption" effect, the transfer efficiency can be improved by applying a lens for the photosensitive layer, the photosensitive layer preferably being at the focal length of this lens. In this way, the light from the optical transmitter / receiver is concentrated at one point in the photosensitive layer, and the variable absorption concentrated at this location will result, largely, in the direction of the optical transmitter / receiver.

Alternatively, for the data transfer from the label to the optical transmitter / receiver, a second optical element in the form of a "Liquid Cristal Modulator", applied in front of or on a (retro) reflecting mirror, can be used, so that the intensity of the light reflected from the mirror can be modulated so as to transfer information from the tag to the optical transmitter / receiver. The latter method, however, requires several process steps in the manufacture of the integrated circuit, on which the necessary circuits and optical components are mounted.

Since bidirectional communication is possible, in addition to identification or transfer of sensor information, other functions can of course also be implemented in the chip 35, such as, for example, "smart card" functions for an electronic exchange, price information and article security information if the labels or the chips 1001553.

-4- are applied to articles. For chips with microprocessor functions, however, a higher energy level is necessary, so that the distance to be achieved will be limited by this.

As a drawback with respect to radio frequency contactless identification labels or chip cards, it can be mentioned that unobstructed visual contact is required between the optical transmitter / receiver and the identification label. However, due to the small distance that can be achieved if the antenna or coil is integrated on the chip, this plays no significant role in the comparison.

The achievable communication distance depends mainly on the energy consumption of the label, the intensity of the transmitter source and whether measures have been taken to separate the transmitter signal and the reflected return signal from each other, for example by means of optical (interference) filters or polarizing flashes.

Naturally, the present identification system 20 can, in addition to an integrated form on one chip, also be built up from separate components for the optical and the electronic elements, whereby greater distances can then be bridged by applying larger optical components.

The present invention will be described below with reference to two figures.

Figure 1 schematically shows a functional diagram of the integrated electronic circuit with liquid crystal modulator, with which all necessary functions of the identification label can be performed, whereby it is of course also possible to omit the information transfer from the transmitter to the card.

Figure 2 schematically shows a functional diagram of the integrated photosensitive layer electronic circuit using variable absorption and reflection by voltage-dependent relaxation and recombination and adding a lens 1001533.

-5- to improve returns.

The integrated label in Figure 1 consists of a photovoltaic element (1), which is connected to an electronic circuit (4) via a diode (2) and power supply capacitor (3). Variation in intensity is applied to the electronic circuit (4) via connection (5), so that information can be transferred from the optical transmitter / receiver to the circuit (4). The output of the electronic circuit (4) is connected via connection (6) to the "liquid 10 crystal" modulator (7), which is arranged in front of mirror (8). The light (9) from the optical transmitter / receiver and any ambient light is received by the photovoltaic element (1), which provides the power supply to the circuit (4) via the capacitor (3). Depending on the transmittance of the liquid crystal modulator (7), the light (10) (11) also originating from the optical transmitter / receiver is received and reflected by mirror (8).

If the mirror (8) is not retro-reflective, the light as drawn in the situation (10) will be reflected. If the mirror (8) is retro-reflective, the light as drawn in the situation (11) in the direction of origin, i.e. the optical transmitter / receiver, will be reflected. Thus, depending on the output signal 25 (6), the intensity of the reflection will vary, so that information from the label can be transmitted to the optical transmitter / receiver.

In the example of figure 2, the function of the photovoltaic element and the modulator is combined in one photoelectric element (12), which provides the power supply of the electronic circuit (4) via diode (2) and capacitor (3) and in which the output (6) is connected to a switching element (13), for example in the form of a "Field Effect Transistor" or PET, with which the load of the element (12) can be varied, with or without the addition of resistor (14) , so that the voltage on this element also varies. Relaxation and recombination will result in 1 0 0 1 5 35 ..

The photoelectric element (12) a variation in the light absorption occurs, whereby the intensity of the reflection depends on the electrical voltage present on the photoelectric element (12). If for the photoelectric element (12) a lens (15) is mounted at a distance equal to the focal length of this lens, the light (16) coming from the optical transmitter / receiver will be concentrated on a certain portion of the photoelectric element (12). The reflected light coming from the same place on the photoelectric element (12) will be returned through the lens (15) in the same direction. Of course, the circuit as shown in figure 2 can also function without the lens (15) being fitted.

1001bio.

Claims (11)

1. A contactless identification system consisting of an optical transmitter and an optical receiver as well as an optoelectronic label, characterized in that the energy supply of the label takes place optically from the optical transmitter, from the environment or from a combination of both, by photovoltaic conversion and in which the energy required for the optical information transfer from the label to the optical receiver is not taken from the amount of electrical energy supplied and converted to the label by optical means, but is directly obtained from the optical energy of the optical transmitter, optionally in combination with other optical sources outside the label. A contactless identification system according to claim 1, characterized in that the optical information transfer from the label to the optical receiver takes place by means of modulation of optical reflection, for example by means of a "liquid crystal" modulator. A contactless identification system according to claim 2, characterized in that the reflection is provided by a retro-reflective mirror, whereby the optical information transfer from the label to the optical receiver takes place only in the direction of the optical receiver. A contactless identification system according to claim 1, characterized in that the optical information transfer 30 from the tag to the optical receiver takes place using voltage-dependent modulation of optical absorption and reflection caused by relaxation followed by recombination of "electron / hole" pairs. I V v *.> - »-8- A contactless identification system according to claim 4, characterized in that a lens is provided in front of the photosensitive layer of the label, such that the photosensitive layer is located at or near the focal length of this lens, so that the light emanating from the optical transmitter one point of the photosensitive layer is concentrated, whereby the retransmitted light from this point is transmitted almost exclusively towards the optical receiver. A contactless identification system according to one or more of the preceding claims, characterized in that information transfer from the optical transmitter to the label takes place by varying the intensity of the light emitted by the optical transmitter. A contactless identification system according to one or more of the preceding claims, characterized in that all optical and electronic components present in the label are integrated on only one optoelectronic chip. A contactless identification system according to one or more of the preceding claims, characterized in that one or more optical filters are used to improve the separation between the light from the optical transmitter and the light from the optical label. (s). A contactless identification system according to claim 8, characterized in that one or more interference filter (s) is used as the filter element. A contactless identification system according to claim 8, characterized in that one or more polarization filter (s) is used as the filter element. 1 ft '* r 7 I v ·>' J \ «'j« -9- A contactless identification system according to one or more of the preceding claims, characterized in that, in addition to or instead of information relating to, for example, the identity of the label, information from sensors connected to the label is also transmitted to the optical transmitter / receiver . 10.1: ·: