Retroreflectors

Claim 1

A system for detecting and locating an objective on the surface of a body of water, comprising: a floating reflective marker having a floating head characterized by being substantially lighter than water, a ballast member secured to said head and dependant therefrom, said ballast member acting with said head to cause the assembly to ride upright in rough or smooth water, the head and ballast member thereby floating upright in water with the upper surface of said head riding above the surface of the water, an upper surface of said head having portions inclined from the horizontal and visible from positions above and laterally removed from said head, a plurality of retroreflectors mounted in said upper surface and distributed angularly around said surface, said retroreflectors having front surfaces to receive a radiation signal and right angled rear reflective surfaces to reflect impinging radiation back at 180° angle from incoming radiation, the front of said retroreflector having at least its surface composed of a hydrophobic material to shed water therefrom, a base station, a source of directed radiation at said station, scanning means to sweep said radiation across an area at a scan rate to cause at least three scan lines of radiation to pass across an area of the size of said floating retroreflector, detection means at said base station to detect radiation reflected from said retroreflector, and signal means to signal the detection of said reflected radiation.

Claim 2

A system for detecting and locating an objective on the surface of a body of water, comprising: a floating reflective marker having a floating head characterized by being substantially lighter than water, a ballast member secured to said head and dependant therefrom, said ballast member acting with said head to cause the assembly to ride upright in rough or smooth water, the head and ballast member thereby floating upright in water with the upper surface of said head riding above the surface of the water, an upper surface of said head having portions inclined from the horizontal and visible from positions above and laterally removed from said head, a plurality of retroreflectors mounted in said upper surface and distributed angularly around said surface, said retroreflectors having front surfaces to receive a radiation signal and right angled rear reflective surfaces to reflect impinging radiation back at 180° angle from incoming radiation, the front of said retroreflector having at least its surface composed of a hydrophobic material to shed water therefrom, a base station, a source of directed radiation at said station, scanning means to sweep said radiation across an area at a scan rate to cause at least three scan lines of radiation to pass across an area of the size of said floating retroreflector, detection means at said base station to detect radiation reflected from said retroreflector, and signal means to signal the detection of said reflected radiation.

Claim 3

A method for detecting and locating a person on the surface of a body of water comprising: positioning on said person an article of apparel having a plurality of retroreflectors mounted in an upper surface thereof and distributed angularly around said surface, said retroreflectors having front surfaces to receive a radiation signal and right angled rear reflective surfaces to reflect impinging radiation back at 180° angle from incoming radiation, directing from an airplane radiation scanned across an area at a scan rate to cause at least three scan lines of radiation to pass across an area of the size of said retroreflectors, receiving and detecting at said airplane radiation reflected from said retroreflectors, and deriving a signal from said reflected radiation to denote the presence of said retroreflectors.

Claim 4

A method for detecting and locating a person on the surface of a body of water comprising: positioning on said person an article of apparel having a plurality of retroreflectors mounted in an upper surface thereof and distributed angularly around said surface, said retroreflectors having front surfaces to receive a radiation signal and right angled rear reflective surfaces to reflect impinging radiation back at 180° angle from incoming radiation, directing from an airplane radiation scanned across an area at a scan rate to cause at least three scan lines of radiation to pass across an area of the size of said retroreflectors, receiving and detecting at said airplane radiation reflected from said retroreflectors, and deriving a signal from said reflected radiation to denote the presence of said retroreflectors.