LASER SYSTEM FOR STANDOFF DETECTION

摘要

A laser system and method employing stimulated Raman scattering using a main laser pulse and a delayed replica reference pulse are provided. A further aspect calculates stimulated Raman loss and stimulated Raman gain from a reflected laser light scatter collected from a fabric or paper specimen. In another aspect, a laser system receives a low energy portion of a spectrum of main and reference laser pulses with a first photodetector, receives a higher energy portion of the spectrum of the main and reference pulses with a second photodetector, and uses a controller to determine a Raman active phonon transfer of energy manifested as an increase in the reflected laser scatter in a lower energy portion of the spectrum and a decrease in a higher energy portion of the spectrum. In yet another aspect, the controller automatically determines if a hazardous particle or substance such as an explosive, is present on a specimen.

主权项

1. A method of using a laser system, the method comprising:
(a) emitting a main laser pulse; (b) shaping the laser pulse which is subsequently used to selectively excite a desired Raman vibration through stimulated Raman scattering, if the associated target is present; (c) creating a delayed replica reference pulse from the main pulse, the main and reference pulses being substantially identical in energy and spectrum; (d) focusing the main and reference pulses; (e) collecting diffuse laser scatter such that relative intensities of at least one spectral half of the scatter generated by each of the main and reference pulses are received and identified by at least one photodetector; (f) calculating stimulated Raman loss and/or stimulated Raman gain from the collected reflected laser scatter; (g) using the calculated value associated with the reference pulse to reduce undesired contributions from the calculated value associated with specimen absorptivity and texture; and (h) automatically determining if a substance trace is present, after at least step (e).