Field coverage configurable passive infrared radiation intrusion detection device

One embodiment of a field coverage configurable passive infrared radiation intrusion detection device comprises a plurality of passive infrared radiation sensors. The device also has an optical element for gathering infrared radiation from different portions of a field and for focusing said infrared radiation onto said plurality of passive infrared radiation sensors. An electrical activation/deactivation circuit receives the output of each passive infrared radiation sensor and selectively activates/deactivates one or more of the plurality of passive infrared radiation sensor outputs thereby configuring the portions of the field covered by the passive infrared intrusion detection device. In another embodiment of a field coverage configurable passive infrared radiation intrusion detection device, the height coverage of the device is adjustable in the field. The device comprises a passive infrared radiation sensor, and an optical element spaced apart from the passive infrared radiation sensor by a separation distance, for focusing infrared radiation from a field at a height distance from the optical element. The device further comprises means for changing the separation distance, thereby changing the height distance of the optical element from the field.

TECHNICAL FIELD

The present invention relates to a passive infrared radiation intrusion detection device whose coverage is field configurable, i.e. the extent of the coverage of the device can be changed at the time of installation. More particularly, the device of the present invention can be field configured laterally or in the height direction, or both.

BACKGROUND OF THE INVENTION

Passive infrared radiation intrusion detection devices are well known in the art. In the prior art, the coverage of a passive infrared radiation intrusion detection device, i.e. the lateral extent of the detection of the device, is set at the factory. Thus, if an installer at a site determines that a particular portion of a field should not be detected, because it has a heat source or otherwise contributes to false alarm, the installer does not have the flexibility to reconfigure the extent of the field coverage for that device.

Further, infrared radiation intrusion detection devices could not be adjusted in the field during installation to take into account different heights.

SUMMARY OF THE INVENTION

Accordingly, in the present invention, two embodiments of a field coverage configurable passive infrared radiation intrusion detection device are disclosed. In a first embodiment, the device comprises a plurality of passive infrared radiation sensors. The device also has an optical element for detecting intrusion in different portions of a field. An electrical activation/deactivation circuit receives the output of each passive infrared radiation sensor and selectively activates/deactivates one or more of the plurality of passive infrared radiation sensor outputs thereby configuring the portions of the field covered by the passive infrared intrusion detection device.

In a second embodiment of the device, the height coverage of the device is adjustable in the field. The device comprises a passive infrared radiation sensor, and an optical element spaced apart from the passive infrared radiation sensor by a separation distance, for focusing infrared radiation from a field at a height distance from the optical element. The device further comprises means for changing the separation distance, thereby changing the height distance of the optical element from the field.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIG. 1there is shown a side view of a first embodiment of a field coverage configurable passive infrared radiation intrusion detection device10of the present invention. The device10comprises a plurality of passive infrared radiation sensors (12A,12B,12C (shown inFIG. 2), and12D). As shown inFIG. 2, each of the sensors12is positioned substantially in a rectilinear formation, i.e. spaced apart by approximately ninety (90) degrees. A single, hemispherically dome shaped, Fresnel lens or other optical element14surrounds the sensors12and gathers the infrared radiation from different portions16(A–D) of the field and focuses them onto the plurality of sensors12(A–D). Of course, it is also within the scope of the present invention that the single optical element14can be replaced by a plurality optical elements with each optical element associated with a different passive infrared radiation sensor12. As shown inFIG. 2, the optical element14is substantially hemispherically domed in shaped and covers the radiation sensors12and houses them. The optical element14also serves to gather the radiation from a plurality of different fields to focus them onto each of the different sensors12.

Referring toFIG. 3there is shown a schematic view of the different portions16of a field covered by the device10. As shown inFIG. 3, the field comprises four different portions:16A,16B,16C and16D. Each of the portions of the fields16is detected by the radiation sensor12with which the field is associated. Thus, for example, if an intrusion were to occur in field16A, the infrared radiation in that field16A would be detected by the radiation sensor12A. Each of the fields16is approximately ninety (90) degrees of a circle, because there are four radiation sensors12covering approximately 90 degrees each.

Finally, referring toFIG. 4, there is shown a schematic circuit diagram of a portion of the detection device10. The output of each of the radiation sensors12is supplied to an electrical activation/deactivation circuit18. In one embodiment, each of the activation/deactivation circuits18(A–D) can be a fuse or a switch. In another embodiment, the plurality of activation/deactivation circuits18(A–D) can be replaced by a microprocessor. The output of each radiation sensor12is supplied to an associated electrical activation/deactivation circuit18which supplies the signals to a multiplex20. The output of the multiplex20goes through a processing circuit, which is well known in the art, to generate an alarm signal. In operation, during the installation of the detection device10, the installer would selectively activate or deactivate each of the circuits18(A–D). For example, if in the field coverage shown inFIG. 3, there is a “hot spot” in the location of the field16D which may cause the generation of a false alarm, the installer can deactivate the circuit18D thereby preventing the output of the radiation sensor12D from reaching the multiplex20. In that event, it would be as if the entire field16D is masked, as shown inFIG. 5and the detection device10would then be nonresponsive to any intrusion occurring in that region16D. The detection device10would respond to an intrusion that occurs in any of the regions16A,16B or16C. When an intrusion occurs in any of those three regions, the sensors12A,12B or12C would generate an output signal which passes through the activation/deactivation circuits18(A–C) to the multiplex20, which passes that signal to the processing circuit to generate the alarm.

From this, it can be seen that with the detection device10, an installer can configure the fields that the detection device10can detect while in the field or during the installation period and can alter the coverage pattern for the detection device10. Of course, the number of fields is not limited to four, which is shown only by way of example, and therefore, any number of sensors12can be used to divide the field into different portions.

Referring toFIG. 6Athere is shown a second embodiment of a detection device110of the present invention. The detection device110is similar to the detection device10, shown inFIG. 1, and therefore like numerals will be used to describe same elements. Similar to the detection device10, the detection device110comprises a plurality of passive infrared radiation sensors12(A–D), but only elements12A and12C are shown, for illustration purposes. In addition, similar to the detection device10, the detection device110comprises an optical element14, which is a substantially hemispherically shaped dome, covering the sensors12, for gathering infrared radiation from different portions of the field and focusing the infrared radiation onto the plurality of sensors12. The radiation sensors12are mounted on a base plate30. The hemispherically shaped optical element14is also mounted on the base plate30. As shown inFIG. 6A, because the optical element14is hemispherically shaped, and is mounted on the base plate30covering the radiation sensors12, it is spaced apart at a distance X as measured in a vertical direction from the apex or zenith22of the hemispherically shaped optical element14to the radiation sensors12. Further, each of the sensors12is mounted on the base plate30such that they receive radiation from a field, shown inFIG. 6B, whose radiation is directed in an angle θ from the horizontal. As a result of this geometry, the hemispherically shaped optical element14gathers the infrared radiation from the field which is at a vertical distance Y from the detection device110. This is shown inFIG. 6B.

The detection device110, however, unlike the device10, is also adjustable in the vertical direction between the sensors12(A–D) and the base plate30. For example, as shown inFIG. 6C, a spacer40can be inserted between the radiation sensors12and the base plate30. Other means for adjusting the distance between the radiation sensors12and the mounting base plate30can be a screw or other adjustable means. By adjusting the distance of the sensors12from the base plate30, the distance X between the apex22of the optical element14and the radiation sensors12is also adjusted. When the distance X is adjusted, it changes the angle θ, from the horizontal, of the radiation which is received from the field and focus onto the radiation sensors12. Thus, the adjustment of the distance X to X′ shown inFIG. 6Cchanges the angle θ to θ′ which changes the distance Y to Y′ as shown inFIG. 6D. Thus, the installer can adjust in the field the vertical distance of the coverage of the detection device110in the field.

Of course, the embodiments shown inFIGS. 1 and 6Acan be further combined into a detection device which is field coverage configurable to change the vertical high as well as lateral fields of coverage.