Infrared intrusion detector and method

An intrusion detector for detecting an intrusion into a protected space overlying a predetermined surface, comprising:

• a housing to be mounted over said surface and including an infrared radiation sensor for sensing moving infrared radiation sources, and a transparent window thereover;
• a plurality of lens elements formed in said transparent window each oriented to receive infrared radiation from a moving infrared radiation source within a predetermined viewing zone of said protected space and to transmit infrared radiation from said source to said sensor;
• an alarm;
• and
• a control system for receiving the electrical output of said sensor and for outputting an alarm signal to said alarm when a moving infrared radiation source is simultaneously detected within at least two of said predetermined viewing zones;
• wherein said control system generates a dynamic alarm threshold for said alarm signal, which alarm threshold dynamically varies according to the environmental noise conditions in the monitored space,
• wherein said control system periodically samples the output of said sensor to produce a plurality of incoming pulses, produces an average of said sensor outputs for a predetermined number of incoming pulses, and utilizes said average of the sensor outputs for generating said dynamic alarm threshold;
• and
• wherein said control system produces an average of said sensor outputs in a dynamic manner for a predetermined number of pulses, by:
• inputting the value of each pulse into a shift register having a plurality of storage locations and operating in a FIFO manner to shift said pulse values from the first storage location to and out of the last storage location;
• and
• with each inputted pulse, adding, to each previously produced average, the value of the pulse inputted into the first storage location minus the value of the pulse outputted from the last storage location.

An intrusion detector for detecting an intrusion into a protected space overlying a predetermined surface, comprising:

• a housing to be mounted over said surface and including an infrared radiation sensor for sensing moving infrared radiation sources and a transparent window thereover;
• a plurality of lens elements formed in said transparent window each oriented to receive infrared radiation from a moving infrared radiation source within a predetermined viewing zone of said protected space and to transmit infrared radiation from said source to said sensor;
• an alarm;
• and
• a control system for receiving the electrical output of said sensor and for outputting an alarm signal to said alarm when a moving infrared radiation source is detected within a viewing zone;
• said control system generating a dynamic alarm threshold for said alarm signal, which alarm threshold dynamically varies according to the environmental noise conditions in the monitored space;
• wherein said control system periodically samples the output of said sensor to produce a plurality of incoming pulses, produces an average of said sensor outputs for a predetermined number of incoming pulses, and utilizes said average of the sensor outputs for generating said dynamic alarm threshold;
• and
• wherein said control system produces an average of said sensor outputs in a dynamic manner for a predetermined number of pulses, by:
• inputting the value of each pulse into a shift register having a plurality of storage locations and operating in a FIFO manner to shift said pulse values from the first storage location to and out of the last storage location;
• and
• with each inputted pulse, adding, to each previously produced average, the value of the pulse inputted into the first storage location minus the value of the pulse outputted from the last storage location.

An intrusion detector for detecting an intrusion into a protected space overlying a predetermined surface, comprising:

• a housing to be mounted over said surface and including an infrared radiation sensor for sensing moving infrared radiation sources and a transparent window thereover;
• a plurality of lens elements formed in said transparent window each oriented to receive infrared radiation from a moving infrared radiation source within a predetermined viewing zone of said protected space and to transmit infrared radiation from said source to said sensor;
• an alarm;
• and
• a control system for receiving the electrical output of said sensor and for outputting an alarm signal to said alarm when a moving infrared radiation source is detected within a viewing zone;
• said control system generating a dynamic alarm threshold for said alarm signal, which alarm threshold dynamically varies according to the infrared noise level in the monitored space;
• wherein said control system periodically samples the output of said sensor to produce a plurality of incoming pulses, produces an average of said sensor outputs for a predetermined number of incoming pulses, and utilizes said average of the sensor outputs for generating said dynamic alarm threshold;
• and
• wherein said control system generates said dynamic alarm threshold by adding, to an initial alarm threshold, an environmental noise factor corresponding to the average of said sensor outputs dynamically produced for said predetermined number of samples.

An intrusion detector for detecting an intrusion into a protected space overlying a predetermined surface, comprising:

• a housing to be mounted over said surface and including an infrared radiation sensor for sensing moving infrared radiation sources, and a transparent window thereover;
• said transparent window being formed with a plurality of lens elements each oriented to receive infrared radiation from a moving infrared radiation source within a predetermined viewing zone of said protected space and to transmit said radiation to said sensor to cause said sensor to produce an electrical output therefrom:
• an alarm;
• and
• a control system for receiving the electrical output of said sensor and for outputting an alarm signal to said alarm;
• said infrared radiation sensor and control system being mounted on a printed circuit board within said housing, which printed circuit board is adjustable with respect to said transparent window by means of a slot formed in the printed circuit board movable with respect to a pin extending through said housing and said slot;
• said pin being rotatable to a first position to free the printed circuit board for adjustment along said slot, or to a second position to lock the printed circuit board in its adjusted position.

An intrusion detector for detecting an intrusion into a protected space overlying a predetermined surface, comprising:

• a housing to be mounted over said surface and including an infrared radiation sensor for sensing moving infrared radiation sources, and a transparent window thereover;
• a plurality of lens elements formed in said transparent window each oriented to receive infrared radiation from a moving infrared radiation source within a predetermined viewing zone of said protected space and to transmit infrared radiation from said source to said sensor;
• an alarm;
• and
• a control system for receiving the electrical output of said sensor and for outputting an alarm signal to said alarm when a moving infrared radiation source is simultaneously detected within at least two of said predetermined viewing zones;
• wherein said control system generates a dynamic alarm threshold for said alarm signal, which alarm threshold dynamically varies according to the environmental noise conditions in the monitored space,
• wherein said control system periodically measures the output of said sensor to produce a plurality of incoming measured signals, produces an average of said sensor outputs for a predetermined number of incoming measured signals, and utilizes said average of the sensor outputs for generating said dynamic alarm threshold;
• and
• wherein said control system produces an average of said sensor outputs in a dynamic manner for a predetermined number of measured signals, by:
• inputting the value of each measured signal into a delay unit having a plurality of storage locations and operating in a FIFO manner to shift said measured signals from the first storage location to and out of the last storage location;
• and
• with each inputted measured signal, adding, to each previously produced average, the value of the measured signal inputted into the first storage location minus the value of the measured signal outputted from the last storage location.