Automatic threat detection based on illumination by penetrating radiant energy using histogram processing

A threat detecting system for detecting concealed threats based on imaging by penetrating radiation comprising:

• an illumination source comprising a flying spot of penetrating radiation,
• conveying means for transporting an object to be inspected through an inspection field swept by said flying spot of penetrating radiation,
• first radiation detecting means, located between said illumination source and said conveying means, for detecting radiation scattered by an object transported through said inspection field and for developing a sequence of scatter signals representative of a sequence of scattered radiation,
• second radiation detecting means located across said conveying means from said illumination source for detecting radiation transmitted by an object transported through said inspection field and for developing a sequence of transmit signals representative of a sequence of transmitted radiation,
• processing means responsive to said sequence of scatter signals and to said sequence of transmit signals for determining whether or not said object poses a threat, said processing means including:
• transmit signal processing means for processing said transmit signals against an attenuation threat criterion,
• scatter signal processing means for processing said scatter signals against a scatter threat criterion, and
• alarm means enabled if either said transmit processing means or said scatter processing means determines said scanned object meets either said transmit or said scatter threat criterion.

A method of identifying a concealed threat using penetrating radiant energy comprising the steps of:

• a) scanning an object with a flying spot of penetrating radiant energy,
• b) developing signals representative of radiant energy scattered by said object in response to the scanning of step a),
• c) producing an intensity distribution of said signals developed in step b),
• d) comparing said intensity distribution of step c) to a limiting characteristic defined for plural intensities;
• e) enabling a first alarm when said intensity distribution exceeds said limiting characteristic for at least one intensity for which said limiting characteristic is defined.