Pet immune intruder detection

An infra-red intruder detector for covering a protected region above a floor plane;

• said detector comprising:
• infra-red sensing means defining a plurality of lower fields-of-view intercepting said floor plane in said region and a plurality of upper fields-of-view extending entirely above said floor plane in said region, said detector having a lower sensitivity to temperature change in said lower fields-of-view compared to said upper fields-of-view;
• and,
• control means coupled to said sensing means for detecting infra-red signals from humans in said lower fields-of-view and rejecting infra-red signals from dogs in said lower fields-of-view.

A passive infra-red intruder detector for issuing an alarm signal in response to temperature differentials between a background and a moving target;

• said detector comprising:
• a sensing element sensitive to infra-red energy;
• optics focusing infra-red energy onto said sensing element from discrete upper and lower fields-of-view, respectively, said detector having relatively greater sensitivity to said temperature differentials in said upper fields-of-view compared to said lower fields-of-view;
• and,
• temperature compensating means for changing said temperature sensitivity as a function of said background temperature in said lower fields-of-view, increasing said sensitivity as said background temperature approaches human skin temperature.

An infra-red intruder detector for covering a protected region having a background temperature and a floor plane;

• said detector comprising:
• at least one pyroelectric sensing element producing electrical signals proportional to temperature differentials between a target in said region and the background temperature of said region;
• optics defining a lower field-of-view intercepting the floor plane and an upper field-of-view extending entirely above the floor plane, said optics focusing infra-red energy onto said at least one sensing element from said upper and lower fields-of-view;
• means for establishing different sensitivities to temperature differentials between the target and the background, said means maintaining said sensitivity in said upper field of view relatively greater than said sensitivity in said lower field-of-view;
• and,
• a temperature sensitivity control adjusting the respective temperature sensitivities in said upper and lower fields-of-view as a function of said background temperature, increasing said respective sensitivities as said background temperature approaches human skin temperature.

An intruder detector including an infra-red detector and a microwave detector covering the same protected area above a floor plane;

• said infra-red detector comprising:
• infra-red sensing means defining a plurality of lower fields-of-view intercepting said floor plane in said region and a plurality of upper fields-of-view extending entirely above said floor plane in said region, said detector having a lower sensitivity to temperature change in said lower fields-of-view compared to said upper fields-of-view;
• and,
• sensitivity means coupled to said sensing means for detecting infra-red signals from humans in said lower fields-of-view and rejecting infra-red signals from dogs in said lower fields-of-view.