WO2008023169A1

WO2008023169A1 - Electronic apparatus dectector

Info

Publication number: WO2008023169A1
Application number: PCT/GB2007/003193
Authority: WO
Inventors: Ronald Smith
Original assignee: Techniscan Ltd
Priority date: 2006-08-22
Filing date: 2007-08-21
Publication date: 2008-02-28
Also published as: GB0616616D0

Abstract

A detection arrangement and method for detecting the operation of electronic apparatus in the vicinity of a detection arrangement is provided. A first plurality of RF frequencies at which a receiver of the detection arrangement receives noise or interference signals in the absence of the operational electronic apparatus is identified. A second plurality of RF frequencies at which emissions from said operative electronic apparatus occur is identified. Each of a third plurality of RF frequencies is listened at, the third plurality of RF frequencies being determined on the basis of said second plurality of RF frequencies but excluding RF frequencies in said first plurality of RF frequencies. The operation of electronic apparatus is detected by reception of a predetermined signal on at least one RF frequency from said third plurality of RF frequencies.

Description

Electronic Apparatus Detector

Technical Field

This invention relates to a device for detecting the presence of electronic apparatus, such as digital cameras or camcorders, when being operated in the vicinity of the device .

Background to the Invention

Operation of electronic apparatus in certain environments may be dangerous, disruptive or illegal. For example, digital cameras or camcorders that record either still or moving images may be used to make unauthorised recordings at public events. This activity is a particularly serious problem for the film industry when camcorders are used in cinemas auditoriums to record newly released films. Illegal copies are then sold to the public with consequential loss to the industry. Another example is the operation of computer equipment during take-off and landing of an aircraft .

In such cases, it is desirable to detect the presence of electronic apparatus in operation. In certain environments, this can be difficult. For example, the small size and quiet operation of modern digital cameras or camcorders make it difficult for cinema security staff to detect and prevent unauthorised use of the devices in the darkness of a cinema auditorium.

Summary of the Invention

Against this background, the present invention provides a method of detecting the operation of electronic apparatus in the vicinity of a detection arrangement, the method comprising: identifying a first plurality of RF frequencies at which emissions from said operative electronic apparatus occur; identifying at least one excluded RF frequency, at which a receiver of the detection arrangement receives noise or interference signals; listening at each of at least one operative RF frequency, the at least one operative RF frequency being determined on the basis of said first plurality of RF frequencies but excluding each of the at least one excluded RF frequency; and detecting the operation of electronic apparatus in the vicinity of the detection arrangement, by reception of a predetermined signal on at least one RF frequency from said at least one operative RF frequency.

Electronic circuits, including the image processors within digital cameras, generate incidental and unwanted electromagnetic radiation. This is sometimes described as noise or spurious emission. These are typically kept as low as possible by the apparatus manufacturers, for instance in order to comply with international laws that set maximum permitted limits on such emissions. The first list of RF frequencies provides information on the spurious emission frequencies characteristic of these electronic circuits. However, other noise or interference, that is not generated by electronic apparatus to be detected, may be received at the specific location. The at least one excluded RF frequency is a list of RF frequencies providing information on frequencies where noise is present, characteristic to the specific location.

Optionally, the step of identifying the at least one excluded RF frequency comprises: listening at each of the first plurality of RF frequencies; detecting a received signal on a frequency from the first plurality of RF frequencies; processing the received signal using a demodulator; and identifying that the at least one excluded RF frequency comprises the RF frequency at which the signal was received, by determining that the demodulated signal comprises a substantially non-DC component.

Spurious emissions may comprise a single frequency carrier, absent of modulation. In contrast, interference signals comprise some form of modulation. The demodulator may comprise at least one of: an amplitude demodulator, a phase demodulator, or a frequency demodulator. The demodulator may comprise more than one of these. In this way, the list of excluded RF frequencies can be determined even when the operative electronic apparatus is in the vicinity of the detection arrangement.

Alternatively or additionally, the at least one excluded RF frequency may preferably comprise at least one frequency at which a receiver of the detection arrangement receives noise or interference signals in the absence of the operational electronic apparatus. An embodiment of the disclosure may therefore be implemented to run a background scan, specific to a location. Such a background scan can be run once, at regular intervals, or as the user demands.

In the preferred embodiment, the third list of RF frequencies is limited to frequencies between 400 MHz and 900 MHz. Optionally, the third list of RF frequencies is limited to frequencies between 400 MHz and 800 MHz. These frequencies have certain propagation characteristics and are used for certain applications.

Also in the preferred embodiment, the electronic apparatus is a portable electronic apparatus and preferably a digital camera, which may include a digital video camera. Then, the first plurality of RF frequencies comprises a plurality of frequencies at which emissions from the digital camera or camcorder occur when the digital camera or camcorder is in operation.

The predetermined signal may be any detectable signal . Additionally or alternatively, detection may comprise identifying that a signal received on at least one RF frequency from said at least one operative RF frequency has a received strength greater than a predetermined value. This predetermined value may be the receiver noise floor level, or it may be some other threshold.

Again, additionally or alternatively, detection may comprise identifying that a signal is received at a first operative RF frequency, as well as that a signal is received at a second operative RF frequency. In this case, the combination of emissions received at at least two frequencies indicates the presence of operational electronic apparatus. Alternatively, the combination of signals received at three or more frequencies may indicate the presence of the operational electronic apparatus.

Optionally, detection of the operation of electronic apparatus may comprise demodulating a signal received on a first operative RF frequency to provide a demodulated signal. Advantageously, when the spurious emission from the electronic apparatus comprises no modulation, the step of detecting the operation of electronic apparatus may also comprise determining that the demodulated signal does not comprise a substantially non-DC component.

Optionally, when the electronic apparatus is a digital camera and the spurious emission comprises modulation, the demodulated signal can be compared with a reference signal . The reference signal may be based on a received optical signal. For example, an optical sensor may be used to receive a similar optical signal to that received by the digital camera. This may allow the detection of a digital camera .

Optionally, the at least one excluded RF frequency is determined on the basis of those frequencies at which a receiver of the detection arrangement receives signals having a strength greater than a predetermined value, in the absence of the operational electronic apparatus. This predetermined value may represent the noise floor of the receiver, or it may be a greater threshold.

Preferably, the detection arrangement further comprises an antenna or aerial coupled to the receiver. Then, the at least one excluded RF frequency is determined on the basis of the signals received by the aerial, and the step of listening comprises receiving signals at the aerial. Hence, the location or design of the aerial may determine the area in which the presence of electronic apparatus is detected.

Advantageously, the received predetermined signal may be a first version of the predetermined signal. Then, a second version of the predetermined signal can be received from the operational electronic apparatus on the at least one RF frequency from said at least one operative RF frequency. This may allow a location for the operational electronic apparatus to be determined on the basis of the first version of the predetermined signal and the second version of the predetermined signal detection. For example, the second version of the predetermined signal may be received using an antenna at a different location or orientation compared with that used to obtain the first version of the predetermined signal . Alternatively or additionally, differences between a timing in the first version and a timing in the second version may be used to obtain a location.

In the preferred embodiment, an alert is provided, to indicate the detection of operational electronic apparatus. This alert may comprise one or both of displaying an amplitude of the received predetermined signal and displaying the demodulated signal .

The present invention may also reside in a detection arrangement for detecting the operation of electronic apparatus in the vicinity of the detection arrangement, the detection arrangement comprising: a processor, configured to identify a first plurality of RF frequencies at which emissions from said operative electronic apparatus occur, and to identify at least one excluded RF frequency at which the detection arrangement receives noise or interference signals; a receiver, adapted to listen at each of at least one operative RF frequency, the at least one operative RF frequency being determined on the basis of said first plurality of RF frequencies but excluding each RF frequency in said at least one excluded RF frequency; and an output, adapted to indicate detection of the operation of electronic apparatus in the vicinity of the detection arrangement, based upon the reception of a predetermined signal on at least one RF frequency from said at least one operative RF frequency.

Brief Description of the Drawings

The invention may be put into practice in various ways, one of which will now be described by way of example only and with reference to the accompanying drawings in which:

Figure 1 shows a schematic diagram of an electronic apparatus detector in accordance with the present invention. Figure 2 shows an example of the physical construction of the electronic apparatus detector of Figure 1, in the form of a hand held instrument .

Figure 3 shows an example of the alternative construction of the electronic apparatus detector of Figure 1, in the form of a fixed device.

Description of a Specific Embodiment

Referring first to Figure 1, a schematic diagram is shown of an electronic apparatus detector. Although the invention is applicable to the detection of any electronic apparatus, for example a portable computer, personal digital assistant (PDA) or digital media player, the embodiments set out herein will refer to a digital camera detector. Similarly, the embodiment set out herein specifies a frequency range of 400 to 900 MHz, although the skilled person will appreciate that the invention may be applicable outside this range.

Electromagnetic radiation 1 from a digital camera that is incident upon aerial 2 is selected and amplified by receiver 3, which is under the control of controller 4.

Aerial 2 may be of a conventional multi element type such as a beam, yagi, log periodic or helical design with dimensions appropriate to use at frequencies from 400 to 900 MHz. This type of aerial has high directional sensitivity, which may be appropriate when the embodiment of the invention is provided in a portable form. Alternatively Aerial 2 may be of a type having low directional sensitivity, for example a folded dipole, which may be appropriate in other circumstances .

Receiver 3 is able to operate at any frequency within the range 400 to 900 MHz, all of or parts of which may be selected or scanned as directed by controller 4. Controller 4 is a computer or microprocessor enabling an operator to control the functioning of receiver 3 by either selecting a predetermined program using appropriate software or manual control as required. Receiver 3 and controller 4 may be a commercially available combined component, for example a radio-scanning device, these are modified according to the required application or they may be designed and constructed specifically for purpose of comparing known camera emissions with emissions detected from within an auditorium. An electronic record or camera database of known camera emissions is used to compare the received signal to the loaded records .

The output from receiver 3 is connected to detector 5 where the received signals are processed. The instrument has an electronic database of camera emissions, which have been previously logged. This database is programmable and comprises a first list of RF frequencies on which emissions from at least one specific camera have been recorded.

Although manufacturers attempt to minimise spurious emissions, it is possible to detect them using a suitably sensitive receiver. Some aspects of these emissions, in particular their frequency distribution and modulation are related to the functioning of the devices that generated them. They can thus be used to help identify the type of camera using generated historic emission records, as contained in the database. This could be known as an electronic identification signature. The frequency distribution, amplitude and modulation of the emissions may be specific to the manufacturer and model of the device. Hence, the database may also comprise information about: the combination of frequencies on which spurious emissions may occur for each camera; the relative amplitudes of spurious emissions; or the modulation of the spurious emissions.

When a digital camera is used in a cinema auditorium its emissions also have some characteristics related to fluctuating ambient light intensity, for example, fluctuations due to image brightness variation or those resulting from the shutter speed of a movie film projector. These characteristics may also be used to assist with the detection of camera use.

Measurements of emissions received in the auditorium are also taken at a time when no electronic apparatus are present that the user might wish to detect. This provides a second list of RF frequencies, which is also stored in an electronic database in the instrument. This pre-installation "site survey" is used to eliminate any local background emissions as these could cause false alarms. For example, the frequency range of 400MHz to 900MHz is used for various radio communications purposes, particularly for the transmission of terrestrial television signals. A digital camera detector must be able to operate in the presence of these TV signals, which are often of high intensity compared with the emission from cameras.

In operation, the receiver 3 scans the list of frequencies from the first list of RF frequencies, but excluding RF frequencies in the second list. For each frequencies, the receiver checks if there are any emissions. The detector processes the output of the receiver to determine if the known camera emissions and detected emissions match then an alarm is activated after a predetermined time period.

Detector 5 can process the output. The output from -receiver 3 is converted, in detector 5, to a dc voltage of level proportional to the amplitude of the received signal . The magnitude of this voltage can be provided to the user. If this voltage exceeds a threshold, an alert can be provided to the user.

The information resulting from such processing can be provided to the user through monitor 8. Monitor 8 allows the user to see the strength of any detected signal and provides the operator with one or more alerts that may provide confirmation that the signal being received originates from a operational digital camera.

Referring now to Figure 2, an example of the physical construction of the digital camera detector of Figure 1, in the form of a hand held instrument, is shown. In this case it is preferable that the instrument has a highly directional sensitivity allowing the operator to determine the direction of the radiation source and hence locate the camera while the operator is seated in the auditorium.

Receiver 3, controller 4 and detector 5 in Figure 1 are contained within a housing 11 to which aerial 2, light sensor 6 an monitor 8 are attached. The whole construction is supported by a handle 12, and in this example shown as a pistol grip. An operator can thus point the aerial in any desired direction whilst observing displays on monitor 8 and hence locate the source of any detected radiation 1 from a digital camera. In this portable form the digital camera detector would typically be powered by batteries and these are contained within housing 11.

Referring then to Figure 3 , an example of the alternative, but presently preferred construction of the digital camera detector of Figure 1 is shown, in the form of a fixed device. Hence, the instrument would have low directional sensitivity and would operate an alarm to summon staff in the event of a camera being detected.

Typically, the embodiment shown in Figure 3 would be an unattended device mounted to an auditorium ceiling above the audience where it would receive radiation from below. The digital camera detector is fixed in such a position as to be able to receive radiation emanating from any position within an auditoriums seating area.

Aerial 2, shown as a folded dipole in this example, and is suspended beneath housing 11 and is surrounded by a reflector 13. This reflector 13 is made of an electrically conductive material, for example thin sheet metal, and is connected to an electrical ground such that it shields aerial 2 from electromagnetic radiation emanating from sources external to the auditorium whilst allowing reception of radiation 1 from sources below. In this fixed form a digital camera detector may operate a remote display 10 located at some distance via a radio or wired link 9. Power for this device may be provided by batteries or by direct wire connection to an external power source.

Whilst specific embodiments have been described herein, the skilled person may contemplate various modifications and substitutions. For example, the skilled person will readily appreciate that forms of alert other than a display may be possible, for instance audio alerts or other visual alerts. Alternatively, the detection arrangement may control other systems on the basis of electronic apparatus being detected, for example switching on the lights in a cinema. The skilled person will appreciate that detector 5 can process the output from receiver 3 in a number of different ways. The following examples, a) to d) , describe four different ways for processing the output. a) The output from receiver 3 is applied to a comparator to determine if the spurious emission has a specific characteristic or characteristics, for example a waveform or periodicity. If the specific characteristic or characteristics are detected, an alert may be provided. b) The output from receiver 3 is applied to a demodulator that detects modulation, for example frequency or amplitude modulation. The resulting signal may be provided as an alert . c) The output from receiver 3, having been demodulated as described in b) , is processed by a high-pass filter to determine if any modulation is present on the received signal . The spurious emissions from the camera may have no discernable modulation. The power of the high-pass filtered signal is measured. If no substantial power is detected, an alert may be provided. d) The output from receiver 3 , having been demodulated as described in b) , is applied to a phased comparator which also receives output from light sensor 6 which is positioned such that incident light 7 from the surrounding environment falls upon it. When the comparator detects synchronicity between variations in incident light 7 and modulation recovered from the received electromagnetic radiation 1 it can provide an alert.

The skilled person will understand that the "site survey" (or background scan) may detect any local background emissions having a signal strength greater than a threshold. The threshold may be the receiver noise floor, or a greater value . The threshold should preferably not be greater than that any threshold used to detect spurious emissions using their signal strength. In an alternative, but presently preferred embodiment, the background scan may scan the range of frequencies to which the list of spurious emission frequencies is limited. Where a signal is received, the signal is demodulated. The demodulated signal is processed by a high-pass filter to determine if any modulation is present on the received signal . The power of the high-pass filtered signal is measured. Interference signals will have modulation, for example in television transmissions. Hence, if any substantial power is detected, the signal may be identified as interference . The frequency at which the signal was received can then be added to the database of interference sources, having the second list of RF frequencies.

In this mode of operation, no pre-installation background scan is required. Instead, the detection arrangement can scan through each of the frequencies on which spurious emissions may occur, as listed in the database of known camera emissions. When a signal is received, it is demodulated and the demodulated signal is analysed. If any modulation is found, then the signal is determined to have come from an interfering source. The frequency at which the signal was received may be added to the database of interference sources. However, if no modulation is found, the signal is determined to have originated from an operational electronic apparatus and an alert may be provided.

It will also be apparent to the skilled person that the electronic database of camera emissions may be built into the detection arrangement, or it may be implemented in firmware. The electronic database of camera emissions may be updateable. If so, a communications port may be provided to the detection arrangement, to allow the database information to be updated.

The skilled person will appreciate that many parts of the detection arrangement may be implemented in one or more of: hardware, firmware, software.

Claims

CLAIMS ;

1. A method of detecting the operation of electronic apparatus in the vicinity of a detection arrangement, the method comprising: identifying a first plurality of RF frequencies at which emissions from said operative electronic apparatus occur; identifying at least one excluded RF frequency, at which a receiver of the detection arrangement receives noise or interference signals; listening at each of at least one operative RF frequency, the at least one operative RF frequency being determined on the basis of said first plurality of RF frequencies but excluding each of the at least one excluded RF frequency; and detecting the operation of electronic apparatus in the vicinity of the detection arrangement, by reception of a predetermined signal on at least one RF frequency from said at least one operative RF frequency.

2. The method of claim 1, wherein the step of identifying the at least one excluded RF frequency comprises: listening at each of the first plurality of RF frequencies; detecting a received signal on a frequency from the first plurality of RF frequencies; processing the received signal using a demodulator; and identifying that the at least one excluded RF frequency comprises the RF frequency at which the signal was received, by determining that the demodulated signal comprises a substantially non-DC component.

3. The method of claim 1 or claim 2 , wherein the at least one excluded RF frequency comprises at least one frequency at which a receiver of the detection arrangement receives noise or interference signals in the absence of the operational electronic apparatus.

4. The method of any preceding claim, wherein the at least one operative RF frequency is limited to frequencies between 400 MHz and 900 MHz.

5. The method of any preceding claim, wherein the electronic apparatus is a digital camera, and wherein the first plurality of RF frequencies comprises a plurality of frequencies at which emissions from the digital camera or camcorder occur when the digital camera or camcorder is in operation.

6. The method of any preceding claim, wherein the predetermined signal is any detectable signal.

7. The method of any preceding claim, wherein the step of detecting comprises identifying that a signal received at at least one RF frequency from said at least one operative RF frequency has a received strength greater than a predetermined value.

8. The method of any preceding claim, wherein the at least one operative RF frequency comprises a first operative RF frequency and a second operative RF frequency, and wherein the step of detecting comprises identifying that a signal is received at the first operative RF frequency and that a signal is received at the second operative RF frequency.

9. The method of any preceding claim, wherein the step of detecting the operation of electronic apparatus comprises: demodulating a signal received at a first RF frequency from said at least one operative RF frequency to provide a demodulated signal .

10. The method of claim 9 when dependent on claim 5, the step of detecting the operation of electronic apparatus further comprising: comparing the demodulated signal with a signal based on a received optical signal .

11. The method of claim 9, wherein the step of detecting the operation of electronic apparatus further comprises: determining that the demodulated signal does not comprise a substantially non-DC component.

12. The method of any preceding claim, wherein the at least one excluded RF frequency is determined on the basis of at least one frequency at which a receiver of the detection arrangement receives signals having a strength greater than a predetermined value, in the absence of the operational electronic apparatus.

13. The method of any preceding claim, wherein the detection arrangement further comprises an antenna coupled to the receiver, wherein the at least one excluded RF frequency is determined on the basis of the signals received by the aerial, and wherein the step of listening comprises receiving signals at the aerial.

14. The method of any of claims 1 to 13, wherein the received predetermined signal is a first version of the predetermined signal, and further comprising: receiving a second version of the predetermined signal from the operational electronic apparatus at the at least one RF frequency from said at least one operative RF frequency; determining a location for the operational electronic apparatus on the basis of the first version of the predetermined signal and the second version of the predetermined signal.

15. The method of any preceding claim, further comprising: providing an alert, to indicate the detection of operational electronic apparatus.

16. The method of claim 15, wherein the step of providing an alert comprises displaying an amplitude of the received predetermined signal.

17. The method of claim 16 when dependent on claim 9, wherein the step of providing an alert comprises displaying the demodulated signal .

18. A detection arrangement for detecting the operation of electronic apparatus in the vicinity of the detection arrangement, the detection arrangement comprising: a processor, configured to identify a first plurality of RF frequencies at which emissions from said operative electronic apparatus occur, and to identify at least one excluded RF frequency at which the detection arrangement receives noise or interference signals; a receiver, adapted to listen at each of at least one operative RF frequency, the at least one operative RF frequency being determined on the basis of said first plurality of RF frequencies but excluding each RF frequency in said at least one excluded RF frequency; and an output, adapted to indicate detection of the operation of electronic apparatus in the vicinity of the detection arrangement, based upon the reception of a predetermined signal on at least one RF frequency from said at least one operative RF frequency.

19. The detection arrangement of claim 18, wherein the receiver is further configured to detect a received signal on a frequency from the first plurality of RF frequencies, the detection arrangement further comprising: a demodulator, arranged, for each frequency from the first plurality of RF frequencies at which the receiver detects a signal, to process the received signal; and wherein the processor is further configured to identify that the at least one excluded RF frequency comprises the RF frequency at which the signal was received, by determining that the demodulated signal comprises a substantially non-DC component.

20. The detection arrangement of claim 18 or claim 19, wherein the at least one excluded RF frequency comprises at least one frequency at which a receiver of the detection arrangement receives noise or interference signals in the absence of the operational electronic apparatus.

21. The detection arrangement of any of claims 18 to 20, wherein the at least one operative RF frequency is limited to frequencies between 400 MHz and 900 MHz.

22. The detection arrangement of any of claims 18 to 21, wherein the electronic apparatus is a digital camera or camcorder, and wherein the first plurality of RF frequencies comprises a plurality of frequencies at which emissions from the digital camera or camcorder occur when the digital camera or camcorder is in operation.

23. The detection arrangement of any of claims 18 to 22, wherein the predetermined signal is any detectable signal .

24. The detection arrangement of any of claims 18 to 23, wherein the processor is further configured to indicate detection on the output by determining that the receiver has received a signal at at least one RF frequency from said at least one operative RF frequency with a received strength greater than a predetermined value .

25. The detection arrangement of any of claims 18 to 24, wherein the at least one operative RF frequency comprises a first operative RF frequency and a second operative RF frequency, and wherein the processor is further configured to indicate detection on the output by identifying that the receiver has received a signal at the first operative RF frequency and that the receiver has received a signal at the second operative RF frequency.

26. The detection arrangement of any of claims 18 to 25, further comprising: a demodulator, arranged to demodulate a signal received at a first RF frequency from said at least one operative RF frequency to provide a demodulated signal.

27. The detection arrangement of claim 26, further comprising : an optical sensor, arranged to receive an optical signal; and wherein the processor is further configured to indicate detection on the output by comparing the demodulated signal with a signal based on the received optical signal.

28. The detection arrangement of claim 26, wherein the processor is configured to detect the operation of electronic apparatus by determining that the demodulated signal does not comprise a substantially non-DC component.

29. The detection arrangement of any of claims 18 to 28, wherein the receiver is further arranged to determine the at least one excluded RF frequency on the basis of those frequencies at which the receiver receives signals having a strength greater than a predetermined value, in the absence of the operational electronic apparatus.

30. The detection arrangement of any of claims 18 to 29, further comprising: an antenna coupled to the receiver; and wherein the at least one excluded RF frequency is determined on the basis of the signals received by the aerial .

31. The detection arrangement of any of claims 18 to 30, wherein the received predetermined signal is a first version of the predetermined signal, wherein the receiver is further arranged to receive a second version of the predetermined signal from the operational electronic apparatus at the at least one RF frequency from said at least one operative RF frequency, and wherein the processor is further configured to determine a location for the operational electronic apparatus on the basis of the first version of the predetermined signal and the second version of the predetermined signal.

32. The detection arrangement of any of claims 18 to 31, further comprising: a display, to indicate the detection of operational electronic apparatus .

33. The detection arrangement of claim 32, wherein the display is arranged to display an amplitude of the received predetermined signal.

34. The detection arrangement of claim 33 when dependent on claim 26, wherein the display is arranged to display the demodulated signal.

35. A method substantially as described herein with reference to Figures 1 to 3 of the accompanying drawings.

36. A detection arrangement substantially as described herein with reference to Figures 1 to 3 of the accompanying drawings . 297685,- sκ_; SK