Importance

Loading Importance Indicators...

Abstract

An improved infra-red lens array for use in a passive infra-red intrusion sensor, which maintains high detection capability for intruders moving in the middle and near field, and yet discriminates well between the movement of intruders and of pets in the near field. The upper part of the lens array is composed of at least one row containing convex lenses, operative to focus the far and middle field radiation of the area to be protected onto the detector of the sensor. The lower part of the array has at least one row containing cylindrical lenses, with their axes of symmetry aligned vertically, operative to focus infra-red radiation from the middle and near fields onto the detector. Each cylindrical lens focuses a vertical curtain of the protected area onto the infra-red detector. In order to ensure reduced sensor sensitivity close to the floor of the protected area, so as to provide pet movement discrimination, the cylindrical lenses are provided with spatially selective attenuation, so as to reduce their transmission factor as a function of the angle between the sensor and points on the floor.

Loading the Abstract Image...

First Claim