WO2011072682A1

WO2011072682A1 - Method of detecting contact between a user's body and an item

Info

Publication number: WO2011072682A1
Application number: PCT/DK2010/000174
Authority: WO
Inventors: Jorn Eskildsen; Daniel Sigrist Christensen
Original assignee: Innotronic Aps; Sigrist Holding Aps
Priority date: 2009-12-17
Filing date: 2010-12-14
Publication date: 2011-06-23

Abstract

There is provided a method of detecting contact between a user's body and an item, the method comprising: providing transmission means capacitively coupled to the user and to ground; providing receiving means to said item capacitively coupled to ground, said receiving means exhibiting a detectable electrical characteristic representing information; and operating the transmission means to pass, across the user's body, a time-varying signal having a magnitude sufficient to be detected by the receiving means when said item is contacted by the user due to the signal becoming both galvanic and capacitively coupled, wherein contact between said user and said item is detected by a phase shift in the signal as it changes from capacitive coupling to a combined capacitive and galvanic coupling.

Description

Method of detecting contact between a user's body and an item

FIELD OF THE INVENTION

The present invention relates to electronic communication, and in particular to the propagation of electrical signals across a user's body through electrostatic coupling. The invention also relates to the use of small currents externally induced in people by electrostatic field coupling.

BACKGROUND OF THE INVENTION

Electrostatic coupling represents a departure from traditional forms of electronic communication, which involve radiated energy. For example, radio-frequency identification (RFID) devices have been employed for some time to remotely sense parameters of interest in people or objects. An RFID device receives a wireless signal from an externally located "reader," which determines the parameter of interest based on the response of the RFID device to the transmitted signal. A simple application of this technology is security: an individual wears an RFID "tag" or badge, and a controlled- entry system unlocks a door only if the wearer's tag is recognized as s/he approaches.

Radiative systems can be configured for a relatively large (i.e., far field) read range. But this capability can actually represent a disadvantage if the environment contains multiple, independent RFID devices, since the reader will excite all devices within the read range simultaneously. Proximately located devices, in other words, cannot share the same frequency channel; separate addressing requires separate frequencies or cumbersome efforts to focus the electromagnetic field from the reader. Magnetostatic and electrostatic RFID systems, by contrast, operate through near-field interaction, and thereby facilitate selective coupling or "channel sharing"; that is, so long as the tagged items are not immediately adjacent (i.e., within a few centimeters of each other), they can be individually addressed. In terms of selectivity, electrostatic systems offer practical advantages in terms of the ease of focusing an electric field as compared with a magnetic field. Electrostatic systems also offer manufacturing and cost advantages, since the induction coil required for magnetostatic systems is eliminated and electrodes can be conveniently and inexpensively deposited on substrates of widely varying shapes and materials.

SUMMARY OF THE INVENTION

The present invention provides method of detecting contact between a user's body and an item, the method comprising:

· providing transmission means capacitively coupled to the user and to ground;

• providing receiving means to said item capacitively coupled to ground, said receiving means exhibiting a detectable electrical characteristic representing information; and

• operating the transmission means to pass, across the user's body, a time-varying signal having a magnitude sufficient to be detected by the receiving means when said item is contacted by the user due to the signal becoming either galvanic or capacitively or both coupled,

wherein contact between said user and said item is detected by a phase shift in the received signal in respect to the transmitted signal as it changes from pure capacitive coupling to a combined capacitive and/or galvanic coupling.

In a preferred embodiment the item is another person. In particular the user could be a health care staff member on a hospital and the other person could be a patient bearing a receiver with a personalised ID tag. In this embodiment physical contact and hence potential contamination will be detected. Specifically this is achieved since the receiving means is provided with an ID tag that is transmitted to the user and detected through second receiving means attached to the user when said user and said person approach and/or contact each other. In such a case the invention provides for an alarm or other means for alerting the health care staff member to perform a hand cleaning manoeuvre. In a particularly preferred embodiment both the healthcare worker and the patient are provided with ID tags allowing two-way communication of IDs. In this respect communication may be carried out wirelessly, such as with an RF signal or inductively coupled signal or optical infrared or other similar wireless communication techniques/systems. The above described embodiment of the present invention also provides for an alarm or other means for alerting the health care staff member to perform a hand cleaning manoeuvre in accordance with the above. In this respect the principles can be used to detect whether or not the healthcare worker has properly washed his or her hands by defining the soap dispenser and the water faucet as items in accordance with the above principles; hence, in order to achieve proper hand cleaning unbroken soap and water columns (outlet flows from the items) must be established in order to obtain the galvanic coupling indicating proper washing. Hence, electrically conductive fluids in general may be used to establish galvanic coupling between a user, such as a healthcare worker, and an item containing the fluids.

As far as the detectable electrical characteristic is concerned impedance is preferred. Preferably the detectable electrical characteristic is oscillatory decay of stored energy. The detectable characteristic may be coupling strength, the coupling strength indicating a distance between the transmission means and the receiving means.

The present invention capacitively transmits not only data but power through a user's body. In one implementation, a transmitter carried by the user transmits power and data to a receiver, which may be carried on another person's body or be part of a grounded item; the return path for the current is provided by environmental ground. The signal that the transmitter applies to the user's body not only contains a data component, but also powers the receiver and enables it to detect and decode the data.

Various strategies for simultaneous transmission of power and data may be employed. In one approach, power and data are simply transmitted at different frequencies. In another approach, the data is transmitted by modulating a carrier from which power is derived. Virtually any modulation scheme can be adapted to the present invention. For example, data may be encoded by frequency modulation of a carrier; the receiver recovers the data by detecting carrier modulations, and derives power from the frequency-varying carrier itself. Alternatively, the data may be encoded by amplitude modulation or phase modulation of a carrier. In still another approach, the data is modulated using, for example, a pseudorandom code to provide spread-spectrum encoding within a broadband carrier, with the carrier again supplying power. And in yet another approach, the data is not actually "transmitted" at all, but is instead imparted to the transmitter by the receiver in the form of loading variations. In the time domain, the temporal pattern of these variations can encode a sequence of bits. In the frequency domain, multiple receivers resonating at different frequencies can impart information merely by their presence or absence, or can instead impart a continuous range of information through variation of resonant frequency (or frequencies).

Furthermore, the coupling of resonators to a transmitter (i.e., a reader) can impart information about their proximity to the transmitter. The coupling strength is inversely proportional to the square of the distance between transmitter and receiver. Receivers having different resonant frequencies can be individually addressed and the coupling strengths separately assessed to obtain distance measurements. Increasing the number of resonators increases the resolution of the measurement (if they lie in a straight line) and the dimensionality of the measurement (if they are not collinear).

In other implementations, the transmitter or the receiver is physically displaced from the user's body (although both receiver and transmitter are coupled to environmental ground), and data and power are transmitted when the transmitter and receiver become sufficiently proximate - via the user's body - to permit capacitive coupling. For example, the transmitter may refrain from sending the data component until alerted (e.g., via a loading measurement) of the coupling to a receiver. In still other implementations, the user may wear more than one receiver. The receivers may also be capable of transmitting data to other receivers. Modulation schemes such as spread-spectrum FM, time-division multiplexing or frequency-division multiplexing facilitate simultaneous operation of multiple transmitters, each using a different modulation parameter.

The invention is amenable to a wide variety of applications, ranging from "interbody" exchange of digital information between individuals through physical contact (e.g., a handshake) to "intrabody" data transfer (e.g., between a paging device worn in the shoe and a wristwatch display device) to devices that permit communication between the user and his or her immediate environment. An important example of the latter category relates to the use of wearable electrostatic devices for security or other purposes. An external reader (i.e., transmitter) may detect data from the tag through loading variations or by reception of a return signal; alternatively, the reader may be carried by the user to identify or discriminate among multiple tagged items (e.g., to determine the tagged contents of boxes in a warehouse). This approach has both cost and weight advantages over conventional RFID. As noted previously, far-field or magnetostatic devices require antennas to transmit or receive radiated magnetic flux. By contrast, because it operates electrostatically, the present invention may utilize small (compared to a wavelength) and arbitrarily shaped electrodes, and no flux-coupling coil is necessary.

By using the body as a medium for signal propagation, i.e., as part of the circuit, the present invention extends the effective range of operation substantially beyond the free- space (i.e., unassisted) coupling distance.

Generally in accordance with the invention, the transmitter and receiver are coupled through a user and room ground. The human body acts as a good conductor capacitively coupling receiver and transmitter. The transmitter, however, produces low- frequency (generally 1 kHz to10 MHz) AC signals that pass, through capacitive coupling, as displacement currents into and from the body of the user, carrying both power and data. Since the transmitter and receiver do not couple with one another directly, the shared room ground provides the return path for the current.

The receiver may include a pair of electrodes, rectification circuitry to convert the power component of the transmitted signal into usable DC, and a detector/demodulator that obtains the data component of the transmitted signal. One of the electrodes is closely coupled capacitively to the user's body so as to receive displacement current passing through the body. The current entering the receiving electrode passes through the rectification and detector circuitry and thereafter to the other electrode, which is asymmetrically coupled capacitively to room ground to complete the circuit path. Due to this asymmetric coupling, a potential difference exists across the electrodes.

Receivers in accordance with the invention generally involve active circuitry that draws power from the transmitted signal in order to support operation. As noted above, however, in some embodiments the receiver circuitry is passive, imparting data through modulation of an electrical characteristic that is sensed by the transmitter.

Another purpose of the invention is to make a safeguarding system and a safeguarding process for portable firearms that release the weapons only for use by authorized persons. Another purpose is to prevent unauthorized persons from firing weapons in an unauthorized manner. In order to eliminate the aforementioned disadvantages of known weapon safeguards, the invention releases the weapons for authorized persons and the blocks of the weapons for unauthorized persons in a reliable and straightforward manner. In particular, the invention releases and blocks operation of weapons in person- dependent manner prior to each individual use, i.e. before each shot. For this purpose the invention enables the release of the weapon in an manner consistent with conventional use of an unsafeguarded weapon. An authorized person only has to perform the actions that are normally required for firing a traditional, non-safeguarded weapons and does not have to perform any other release actions. Similarly, the invention blocks the weapon without additional steps, so that an unauthorized person who operates the weapon in traditional manner is unable to fire a shot.

Moreover, the present invention features a keyless entry system for locked doors, including signal generating means that are carried by a person. A signal with a predetermined frequency characteristic is generated with sufficient strength such that the generated signal is transmitted through the carrier's body. There are receiver means including detector means for detecting a signal with the predetermined frequency characteristic and engagement means that are engageable by the carrier's body for providing signals transmitted through the body to the detector means. There are means responsive to the detector means for unlocking the door when a signal having the predetermined frequency characteristic is detected.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a generalized representation of intra-body and inter-body power and data transmission in accordance with the present invention, reflecting capacitive coupling of displacement current into the body and the use of the environment as the current return path. The schematic arrangement shown in FIG. 1 is valid for both intrabody and interbody modes of capacitive coupling. In the figure, a transmitter applies an AC signal to the body of a user via capacitive coupling, represented as a capacitance. This signal passes through the user's body to a receiver mounted on another person's body; before contact via a capacitive electrostatic linkage, and upon contact via both a capacitive electrostatic linkage and a galvanic linkage (i.e. the signal becomes both capacitively and/or galvanically coupled resulting in a phase shift). The transmitter and receiver are all capacitively coupled to the ambient ground. The respective capacitances can be a combination of air and earth ground, and materials in the vicinity of the persons can contribute. Generally, the noted capacitances are on the order of 1 -10 pF. Not shown in the figure are various parasitic capacitances. These are usually negligible but, depending on the configuration, can interfere with operation.

Specfically in FIG. 1 a transmitter (1 ) is connected to a plate capacitor (2) embedded in a shoe warn by person 1. The transmitter excites the plate capacitor with an AC voltage signal at a specific frequency controlled by the connected computer (5). By means of this arrangement person 1 now emits an AC electric field (E) throughout the entire body to the surroundings.

Person 2 is connected to a plate capacitor (4) embedded in a wrist watch. The signal picked up by plate capacitor (4) is fed to a receiver (3), which amplifies the desired frequency of interest. This signal is then fed to a PC (5) for further processing and displaying the signal picked up.

Fig. 2 shows a graphical simplified representation of the signal transmitted (1 ), the signal received before skin contact (2) and the signal received after skin contact (3). As seen in fig. 2. a phase shift in the received signal is observed in respect to the transmitted signal (1 ), when person 1 touches (makes skin contact to) person 2.

In an interbody coupling configuration, the transmitter in the first person is physically displaced from the second person. The second person becomes electrostatically coupled to first person (equipped with transmitter electrode) as she/he approaches. Without the human body as an electrostatic conduit, capacitive coupling between the transmitter and receiver would be negligible unless brought within centimeters of each other. The body effectively extends the coupling range. When the bodies become contacted the signal changes phase, which is used to send an ID signal from the patient back to the healthcare worker.

In an alternative approach, the user's body is employed as a two-way transmission channel, and the worn device actually transmits information (rather than simply modulating detectable electrical characteristics). The system may also be used as a position-sensor, with an array of multiple receivers determining the position of the person based on the relative strengths of the received signals coupled out of the person. Since the signals are not transmitted as radiated energy, small and essentially flat electrodes may be used in the transmitters and receivers. These electrodes efficiently couple to the user by virtue of their surface area and can, for example, be readily incorporated into a watch, a credit card sized component, a shoe, and so forth. In a preferred embodiment, a transmitter carried by the user passes signals to one or more nearby receivers carried by other users or located in fixed positions. In the quasi- electrostatic field produced by the transmitter the user is capacitively coupled to the receivers through the atmosphere. Accordingly, the user need not physically contact the receivers to pass information to them. For example, two users shaking hands may transfer information between transmitters and receivers they each carry. The proximity of the hands provides a conductive path for the signal current. The return path can be a combination of air and earth ground.

The system may include a portable, scalable receiving device that consists of an array of orthogonal electrodes that are, respectively, connected to receivers. A processor connected to the receivers determines, based on the signals received by the individual receivers, the relative position of the user. The electrodes are extended or collapsed, as necessary, to accommodate the relative scale of the user's physical movements to the movements of the user within, for example, the three-dimensional virtual space displayed on an associated screen.

The present invention is also applicable as a system for personal activation of a weapon. The approach underlying the invention is to assign unique, personal user data to any person who is authorized to use a given weapon or to two or more persons for their joint use of one or more weapons. The weapon stores user data in a memory. In order to release a weapon, that user data must be supplied to the weapon by the intended user. An authorized user is equipped with a transmitter to transmit his or her user data to the weapon. Transmission is by physical contact with the weapon. The contact which is necessary for the transmission of user data requires no additional action on the part of the user. Consequently the transmission of the user data for releasing the weapon, and the verification of said user data as to whether the current user is an authorized user for that particular weapon, is action-integrated. In other words, the process is carried out intuitively by the respective user. Prior to each discharge of the weapon, the invention transmits user data to the weapon and the weapon verifies the user data. Therefore, an unauthorized person cannot use a weapon equipped with the invention, even if the weapon was used immediately beforehand by an authorized person. In the case of automatic weapons, which are able to fire several shots in succession when the discharging mechanism is actuated, the release, in accordance with the invention, of the weapon takes place prior to each actuation of the discharging mechanism.

Claims

1. A method of detecting contact between a user's body and an item, the method comprising:

• providing transmission means capacitively coupled to the user and to ground;

• operating the transmission means to pass, across the user's body, a time-varying signal having a magnitude sufficient to be detected by the receiving means when said item is contacted by the user due to the signal becoming galvanic and/or capacitively coupled,

wherein contact between said user and said item is detected by a phase shift in the signal as it changes from capacitive coupling to a combined capacitive and/or galvanic coupling.

2. The method of claim 1 , wherein the item is another person.

3. The method of claim 2, wherein the receiving means is provided with an ID tag that is transmitted to the user and detected through second receiving means, optionally attached to the user, when said user and said person approach and/or contact each other.

4. The method of claim 3, wherein the user is a healthcare worker, who upon contacting the other ID tagged person is alerted or alarmed with a view to perform a handcleaning manoeuvre.

5. The method of claim 1 , wherein the detectable electrical characteristic is impedance.

6. The method of any one of the preceding claims, wherein the detectable characteristic is coupling strength, the coupling strength indicating a distance between the transmission means and the receiving means.

7. The method of any one of the preceding claims, further comprising the step of operating the receiving means to vary the detectable electrical characteristic in a manner indicative of information, the transmission means detecting the variations to recover the information.

8. The method of any one of the preceding claims, wherein the item is a gun, which will only be activated upon receiving a coded signal from the user.

9. The method of any one of the preceding claims, wherein the item is a fluid dispensing apparatus, such as a soap dispenser or a faucet, with a vertical continuous flow of fluid, wherein contact between the user and the item is established when the user contacts the fluid.

10. The method of claim 9, wherein the receiver of the item wirelessly transmits a signal to the second receiver.

11. The method of claim 10, wherein the signal includes information about the duration of contact between the user and the fluid dispensing apparatus.