Patent ID: 8842015

Claim:
A method of detecting reflectors within a field of vision, comprising: providing a sensor body having an electromagnetic transceiver for sending and receiving an electromagnetic signal, said sensor body further having a comparator, a timer and an alarm signal; said transceiver sending an electromagnetic signal downrange to an area of interest; said transceiver receiving a reflected signal comprising in part the sent electromagnetic signal; said timer determining the signal elapsed time between the transceiver sending the signal downrange and receiving the reflected signal back at the transceiver, wherein the transceiver sending the signal is defined as the start time; generating signal strength threshold values which vary with the signal elapsed time based on an expected reflected signal intensity that would be received at the transceiver from background, ambient surfaces having no highly reflective surfaces, reflectors or retro-reflectors within the field of view of the transceiver out to the distance that could have been detected by the transceiver within the respective elapsed time; said sensor comparator comparing the intensity of the reflected signal against the generated signal strength threshold value for the determined signal elapsed time; said sensor comparator triggering the alarm signal when said reflected signal is greater than said generated signal strength threshold value, wherein said alarm signal is one of the group of an audible signal, a visual signal, movement of a mechanical device or a vibratory signal to signal the presence of one of a highly reflective surface, a reflector or a retro-reflector within the field of view of the sensor; and said sensor comparator turning off the alarm signal when said reflected signal is less than said generated signal strength threshold value, wherein said alarm signal is one of the group of an audible signal, a visual signal, movement of a mechanical device or a vibratory signal to signal the absence of any highly reflective surface, reflector and retro-reflector within the field of view of the sensor.