Wide-angle motion detector with close-in, prismoidal reflector

摘要

A passive infra-red motion detector with wide field of view extending to greater than 180 degrees that can be achieved in a cost-effective manner using a single sensor. The motion detector includes a generally prismoidal infra-red mirror having two angled reflecting surfaces forming an apex, which apex may be truncated. The prismoidal reflecting surfaces and their apex are positioned close to and overlying at least a portion of the motion detector sensor and the apex is spaced apart from the sensor at most a distance comparable to a characteristic transverse dimension of the sensor. Because of the close proximity of the mirror to the sensor, the area of the reflecting surfaces need not be very large and may be made comparatively small. The mirror surfaces deflect infrared energy from a suitable arrangement of lenses or other focusing elements onto the sensor from a plurality of zones so as to extend the lateral extremities of the motion detector field of view. Configured in this way, motion detectors may be provided with viewing angles at least up to 220 degrees using a single sensor. In its overlying position the mirror head obstructs at least a portion of the sensor. Another portion of the sensor may be left unobstructed, and additional reflecting or focusing surfaces may also be provided on the same mirror head for directing radiation to the unobstructed sensor portion. The mirror head may be formed together with a base from a single member, which also is shaped to receive and hold an integrated-circuit sensor package. The unitary mirror head and base portion can be mounted directly on a printed circuit board and the mirror is automatically aligned correctly over the sensor.