Patent ID: 7161152

Claim:
A motion detection system comprising: a first sensor sensitive to light in a first range of wavelengths in at least one detection zone and generating a first output signal representative of the detected level of light in said first range; a second sensor sensitive to light in a second range of wavelengths, different from said first range, and generating a second output signal representative of the detected level of light in said second range, said second sensor being positioned proximate said first sensor; and a processor, said processor comparing said first output signal to a first threshold value and said second output signal to a second threshold value, said processor programmed to generate an alarm signal based upon said first and second output signals, whereby said alarm signal is generated when first and second conditions are satisfied, said first condition being satisfied when said first output signal exceeds said first threshold value at a first time, and said second condition being satisfied when said second output signal does not exceed said second threshold value beginning at a second time, said first and second times separated by no more than a predetermined amount of time.