Abstract
The authors have developed a compact system for finding intruders using a holographic diffraction grating which is called the Rotary Hologram Disk (RHD). The system is installed in a room on the ceiling with the surface of the RHD parallel to the floor. An IR laser beam is projected downward perpendicularly onto the RHD, and it is diffracted in two directions. The RHD rotates at a constant speed, and the diffracted beams scan the room along the two circular cones. The scanning beam light is reflected by the wall, the floor, the fixtures and the human body, and then returns to the system. By comparing the scattered light intensity with the reference data, the existence of the human bodies is detected. An example of operations of the system is described, and its merits and limitations are discussed.
