Motion detector for space surveillance
First Claim
1. A motion detector responsive to incident radiation, comprising:
- an elongate four-sided frustopyramidal box with a first pair of longitudinal walls bisected by a plane of symmetry and a second pair of longitudinal walls converging toward said plane of symmetry from a wider closed end toward a narrower entrance and accessible to incident radiation, at least the walls of said second pair having reflective inner surfaces;
a concave radiation reflector at said closed end with a vertex in said plane of symmetry and a focus near said entrance end; and
radiation-sensing means in the vicinity of said focus confronting said concave reflector for illumination by incident beams of parallel rays approaching said entrance end at a plurality of predetermined azimuthal angles with reference to said plane of symmetry and reflected at least once in said box by a wall of said second pair, said radiation-sensing means having a receiving area substantially narrower than said entrance end at least in a direction perpendicular to said plane of symmetry, the length of said box being so related to the angle of convergence ∝
included between said second pair of walls and said plane of symmetry that incoming beams traversing said entrance end at azimuthal angles ±
(2n+1)·
α
undergo n reflections at said second pair of walls before reaching said concave reflector, n being an integer ranging from 0 to a maximum of 3, said incoming beams being converted by said concave reflector into converging beams undergoing each a further reflection at said second pair of walls before impinging from different directions onto said radiation-sensing means.
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Accused Products
Abstract
A motion detector responsive for infrared radiation, e.g. to use in burglar-alarm installations, comprises an elongate frustopyramidal box with an entrance opening at one end, a concave mirror at the opposite end and four flat, internally reflecting longitudinal walls, two of them converging toward the entrance end on opposite sides of a plane of symmetry with which they include an angle between about 8° and 15°. A pyroelectric radiation sensor near the entrance end, lying in the vicinity of the focal point of the concave mirror, is disposed for illumination by beams of parallel rays in a limited number of fields of view; these beams approach the entrance end at different azimuthal angles, included with the preferably vertical plane of symmetry, but occupy closely adjoining regions inside the box. A planar deflector at the entrance end, bisected by the plane of symmetry, also establishes a limited number of elevational angles for the beams focused upon the radiation sensor.
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Citations
13 Claims
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1. A motion detector responsive to incident radiation, comprising:
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an elongate four-sided frustopyramidal box with a first pair of longitudinal walls bisected by a plane of symmetry and a second pair of longitudinal walls converging toward said plane of symmetry from a wider closed end toward a narrower entrance and accessible to incident radiation, at least the walls of said second pair having reflective inner surfaces; a concave radiation reflector at said closed end with a vertex in said plane of symmetry and a focus near said entrance end; and radiation-sensing means in the vicinity of said focus confronting said concave reflector for illumination by incident beams of parallel rays approaching said entrance end at a plurality of predetermined azimuthal angles with reference to said plane of symmetry and reflected at least once in said box by a wall of said second pair, said radiation-sensing means having a receiving area substantially narrower than said entrance end at least in a direction perpendicular to said plane of symmetry, the length of said box being so related to the angle of convergence ∝
included between said second pair of walls and said plane of symmetry that incoming beams traversing said entrance end at azimuthal angles ±
(2n+1)·
α
undergo n reflections at said second pair of walls before reaching said concave reflector, n being an integer ranging from 0 to a maximum of 3, said incoming beams being converted by said concave reflector into converging beams undergoing each a further reflection at said second pair of walls before impinging from different directions onto said radiation-sensing means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification