ALARM OPTICAL DEVICE Russian patent published in 1994 - IPC

FIELD: protective signalling devices. SUBSTANCE: zone under protection is irradiated by infrared pulses and reflected rays are detected by Fresnel mirror 1 and directed to two-plate photodetector 3. Optical axis of radiator is brought in coincidence with optical axis of Fresnel mirror 1. Photodetector 3 is placed on optical axis of Fresnel mirror 1 in parallel with the axis. Division line of adjacent plates of photodetector 3 is set in focus of place of protected zone. Electrical part ensured signalling when intruder appears in protected zone, or behind or before the zone. EFFECT: enhanced functional reliability of device. 2 dwg