DE2919158A1 - Contactless object identification using electro-decoded cards - has metal strip lengths tuned to alternating field component frequencies - Google Patents

Abstract

The device is for identifying objects and has a transmitter producing an alternating electromagnetic field, a receiver for the field, and identification cards for attachment on the objects having metal strips affecting the field when placed in it. The cards are small and light and the identification takes place without contact between card and reader. The transmitter (SE1) produces a field made up of several frequencies. Each card has metal strips of different lengths tuned to different field frequencies. The receiver (EM1) determines which field frequencies are affected by the insertion of a partic. card and forms an object identity code from these frequencies. The effective lengths of the metal strips can be varied by length variations of permanent magnetic layers partially covering them.

Description

Device for identifying objects

The invention relates to a device for identifying objects with a transmitter generating an electromagnetic alternating field, a receiver for the alternating field and with identification cards to be attached to the objects, which, when introduced into the alternating field, have metal strips which influence it.

It is known that at access controls, self-service bank counters, Self-service petrol stations etc. to identify people by the fact that they insert their machine-readable ID cards into a reader that reads the ID card controlled. Postal codes are also machine-readable for sorting letters the letters printed.

Because of this addressing, the route of the letter is automatic controlled. Freight wagons can be identified by having a Identification device is attached, which is driven by an HF loop on the track Energy is supplied, which in turn is a combination of certain frequencies sends out, by means of which the wagon is identified. These are knew Facilities have the disadvantage that the markings either only in immediate Contact can be read by a reader or that the effort for the Marking relatively large and the facilities too heavy and for many applications are unwieldy.

It is also known to detect unauthorized removal of objects from rooms each monitored object with a metal strip made of suitable material and with certain dimensions and at the exit of the room to generate a high-frequency field.

If an object marked in this way is brought into this field, so it is changed by the resonance oscillation of the metal strip in such a way that a receiver can determine this. To release the object, the strip can by means of a Permanent magnets are influenced in such a way that the HF field no longer changes significantly will. In this way, you can choose between authorized and unauthorized removal of Objects can be distinguished, but identification is not possible.

The present invention is based on the object of a device to create with the objects with the help of a small and light weight attached to them Identification card can be identified without the identification card must be brought into direct contact with a reader.

According to the invention this object is achieved in that the transmitter an alternating field having n frequencies is generated and the identification cards each have several metal strips of different lengths, which are based on frequencies of the alternating field are matched, and that the receiver when introducing a Identification card determined in the alternating field influenced frequencies and from These frequencies form a code signal identifying the object.

Of the n frequencies contained in the high-frequency field, affects individual frequencies. In total there are 2n different combinations of metal strips, so that if you take into account that an identification card is not usable without a metal strip, identifies 2n-1 different objects without contact with a reader or the like necessary is. In general, however, you will use a secure code, so that only one smaller number of objects can be identified.

The identification card can be an identity card for persons or also be a sticker or the like for objects. You don't need to be stiff to be, but at least when they are in the high-frequency field for identification is brought to be curved only so much that the resonance frequency of the metal strip is not changed significantly. The new facility can be used in retail outlets Not only can it be used as protection against theft, but it can also be used by Evaluation of the affected frequencies immediately reveals the true number and the price for invoicing and warehousing.

All n frequencies of the high-frequency field can be present at all times be, they could = but also be run through one after the other, with the run be carried out cyclically or triggered by a sensor that detects an object can. The receiver evaluates the influence according to the frequency generation the frequency through the metal strips in parallel or in chronological order.

For easy adjustment of the metal strips to the desired resonance frequencies the metal strips can be made magnetic by combining them with a hard magnetic layer can be influenced.

With reference to the drawing, the invention and others are described below Advantages and additions described and explained in more detail.

FIG. 1 shows the circuit diagram of an exemplary embodiment with parallel Emission of all frequencies of the high frequency field, Figure 2 an identification card and FIG. 3 shows an embodiment with serial transmission of the frequencies.

In Figure 1, SEI denotes a transmitter arrangement, the n transmitters SF1, SF2, SF3, .. SFn, which emit different frequencies. The composite signal is fed to a transmitting antenna SA, which thus emits a high-frequency field, which consists of components with different frequencies. This high frequency field is received by a receiving antenna EA, to which a receiver arrangement EM1 is connected, which contains n selective receivers EF1, EF2, EF3 ... EFn, the are tuned to the frequencies of the transmitters SF1, SF2 ... B. the recipient EF1 to the frequency of the transmitter SE1, the receiver EF2 to the frequency of the transmitter SF2 etc. In the normal case, if the field between the transmitting antenna SA and the receiving antenna EA is not disturbed, the selective receivers EF1, EF2 ... each receive about same signal amplitude. These signals are rectified in the selective receivers, and the rectified signal is via a threshold value stage of an evaluation unit AW1 supplied.

Becomes in the electromagnetic field emitted by the antenna SA brought an object OB in which an identification card IK contained with metal strips that are tuned to frequencies used by the transmitter SEI broadcast are the corresponding components of the electromagnetic field influenced, and the signal amplitudes received by the receiver arrangement EM1 of the individual components are different. The evaluation unit AW1 is therefore a combination of signals is supplied from which the length of the on the identification card IK attached metal strips can be recognized. The object OB is thus identified.

In Figure 2, the identification card IK is shown schematically. In addition to an unmarked print in plain text, a passport photo or the like six metal strips Ml, M2 ... M6 be attached.

These have different lengths and form i / 2 resonators for different frequencies of electromagnetic fields. Length differences of 1 are completely sufficient in view of the circular quality of such resonators, so that with ten metal strips, corresponding to around 1000 identifiable objects, one Bandwidth of only 0.1 is required. In the embodiment of Figure 1 are only the metal strips M1, M3, M6 are available, the other possible metal strips M2, M4, M5 are shown in dashed lines. Elsewhere on the identification card IK can be attached additional metal strips that are perpendicular to the ones shown and are the same length as this one. With such an arrangement achieved that the sensitivity of the device according to the invention is largely independent from the position of the identification card IK to the high frequency field. Instead of this or in addition to this, it is also possible not to use a linearly polarized high-frequency field, but to use a circularly polarized one.

Especially when a large number of objects can be identified should be, the arrangement of Figure 1 requires a lot of effort, since with the Number of iden- verifiable objects the number of senders and the selective recipient increases. Figure 3 shows an arrangement in which the individual Frequencies are output serially, so that only a single transmitter SE2, its Frequency must be controllable, and a receiver EM2 whose bandwidth depends on the number the objects to be identified are required. To the recipient SE2 an antenna designed as a loop SL is connected. A separate receiving antenna is not provided because the EM2 receiver directly loads the antenna SL measures. The transmitting and receiving antenna arrangement could of course also be used the circuit of Figure 2 can be used. The antenna arrangement could also be the FIG. 3 can be used in the circuit according to FIG.

The transmitter SE2 receives the signal to control its frequency an amplifier V, which is connected to a digital-to-analog converter with resistors RO, R1 ... R5, R6 is connected. This digital-to-analog converter sets the standard of one Ring counter RZ, which is controlled by a clock TG, in a for control of the transmitter SE2 to a suitable signal. The ring counter RZ has as many levels as different frequencies are to be generated and thus how different Lengths of metal strips are provided. There is only one level of the ring counter at a time RZ set. Gate circuits T1, T2 ... T6 are also connected to the ring counter stages, which the rectified input signal passed through a threshold value stage of the receiver EM2 is supplied.

Is z. B. the first stage of the ring counter RZ is set, then from Voltage divider R1, RO generates a control signal for the transmitter SE2, which the Transmitting a first frequency causes. Depending on whether the identification card 1K contains a metal strip whose resonance frequency is equal to this first frequency is, the gate circuit T1 outputs log.-t'1 "or" O "signal second Level of the ring counter RZ is set, a second is via the voltage divider R2, RO The control signal is sent to the transmitter SE2 and the second gate circuit T2 is prepared, their output signal again, depending on whether a corresponding metal strip is on the identification card IK is attached, emits 2 or fO "signal. Are all If the stages of the ring counter RZ go through, the gate circuits T1, T2 ... T6 have one Signal combination issued, which is attached to the information card 1K Metal strip corresponds. This signal combination can be used in an evaluation circuit AW2 can be saved and evaluated.

Claims (4)

Claims 1. Device for identifying objects with a transmitter generating an electromagnetic alternating field, a receiver for the alternating field and identification cards to be attached to the objects, which have metal strips influencing it when introduced into the alternating field, d a d u r c h e k e n n z e i c h -n e t that the transmitter (SE1, SE2) has n frequencies having alternating field generated and the identification cards each have several metal strips have different lengths, which are matched to frequencies of the alternating field are, and that the recipient when introducing an identification card (IK) determined in the alternating field influenced frequencies and from these frequencies forms the code signal identifying the object. 2. Device according to claim 1, d a d u r c h g e -k e n n z e i c h n e t that the transmitter (SE1) the alternating field components of different frequencies outputs in parallel. 3. Device according to claim 1, d a d u r c h g e -k e n n z e i c h n e t that the transmitter (SE2) the alternating field components of different frequencies outputs serially. 4. Device according to one of claims 1 to 3, d ad u r c h g e it is not indicated that the metal strips (M1, M2 ... M6) are used for setting their effective length at least partially with a permanent magnetic layer are coverable.