Motion detector for detecting tampering and method for detecting tampering
A motion detector for detecting a tampering within a detection zone. A vibration-sensing unit sensitive to vibrations applied to the detector is provided to produce a vibration output signal representative of a detected parameter of the vibrations. A light-sensing unit sensitive to light in a predetermined spectrum is provided to produce a light output signal representative of a detected parameter of the light in the predetermined spectrum. A processing unit is further provided to determine if the vibration output signal is consistent with a predetermined model indicative of a tampering and producing an activating signal accordingly.
1. A motion detector for detecting a tampering of the motion detector, comprising:
a lens;
a vibration-sensing unit sensitive to vibrations applied to the detector lens and producing a vibration output signal representative of a detected parameter of the vibrations;
an infrared light-sensing unit sensitive to infrared light in a predetermined spectrum and producing a light output signal representative of a detected parameter of the light in the predetermined spectrum; and
a processing unit for determining if the vibration output signal is consistent with a predetermined model indicative of a tampering and producing an activating signal accordingly.
2. The detector of claim 1 , further comprising a signal amplifier for amplifying the vibration output signal and a signal filter for filtering the vibration output signal.
3. The detector of claim 1 , wherein the detected parameter of the vibrations comprises at least one of frequency, amplitude and intensity of the vibrations.
4. The detector of claim 1 , wherein the vibration-sensing unit and the light-sensing unit are integrated into a unitary section, which is made of materials inherent with pyroelectric-effect and piezoelectric-effect.
5. The detector of claim 4 , wherein the unitary section is a pyroelectric sensor responsive to infrared light and vibration.
6. The detector of claim 1 , wherein the vibration sensing unit is selected from the group consisting of a piezo-electric transducer, an electret microphone, any type of microphone and an accelerometer.
7. The detector of claim 1 , wherein the light-sensing unit is a pyroelectric sensor sensitive to light in the infrared spectrum.
8. The detector of claim 1 , wherein the predetermined model indicative of a tampering comprises a tampering pattern indicative of a spraying, the tampering pattern comprises a tampering alarm threshold empirically generated and indicative of a spraying, and the processing unit compares the vibration output signal with the tampering alarm threshold and produces an activating signal indicating a spraying if the vibration output signal exceeds the threshold.
9. The detector of claim 1 , wherein the predetermined model indicative of a tampering comprises a tampering pattern indicative of a brushing, the tampering pattern comprises a tampering alarm threshold empirically generated and indicative of a brushing, and the processing unit compares the vibration output signal with the tampering alarm threshold and produces an activating signal indicating a brushing if the vibration output signal exceeds the threshold.
10. The detector of claim 1 , wherein the predetermined model indicative of a tampering comprises a tampering pattern indicative of an application of a film onto lens of the detector, the tampering pattern comprises a tampering alarm threshold empirically generated and indicative of an application of a film on the lens of the detector, and the processing unit compares the vibration output signal with the tampering alarm threshold and produces an activating signal indicating an application of a film onto the lens if the vibration output signal exceeds the threshold.
11. The detector of claim 1 , further comprising at least one lens or window that is transmissive or reflective of the wavelength in the visible or near infrared and an active visible or near infrared sensing unit for detecting presence of or application of mask materials in the vicinity of the lens or window.
12. The detector of claim 1 , further comprising a microwave sensing unit for detecting the presence of or application of materials that block far IR energy.
13. A method of detecting a tampering of a motion detector, comprising the steps of:
providing a lens;
sensing vibrations applied to the lens and producing a vibration output signal representative of a detected level of the vibration; and
determining if the vibration output signal is consistent with a predetermined model indicative of a tampering and producing an activating signal accordingly.
14. The method of claim 13 , wherein producing a vibration output signal representative of a detected level of the vibration comprises producing a vibration output signal representative of at least one of frequency, amplitude and intensity of the vibrations.
15. The method of claim 13 , wherein determining if the vibration output signal is consistent with a predetermined model indicative of a tampering and producing an activating signal accordingly comprises determining if the vibration output signal is consistent with a tampering pattern indicative of a spraying and producing an activating signal indicating a spraying accordingly.