US 6,115,123 AGranted

Holographic laser aimpoint selection and maintenance

AssigneeNorthrop Grumman Corporation

InventorsEddy A. Stappaerts, William H. Long, Jr.

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Abstract

The present invention relates to a laser pointing and tracking system which forms and maintains a small laser spot size at a selected aimpoint on a target and compensates for optical distortion in the intervening media. The invention comprises an illumination laser for directing a first wide divergence beam of short-pulse laser radiation toward a stationary or moving target. The target reflects a portion of the incident beam as return radiation which is interfered with a properly-timed short-pulse reference beam on an electronic radiation detector array. The detector array signals are processed to produce an electronic hologram which is imposed as a phase pattern on a spatial light modulator. A laser reads out the hologram to direct a beam of radiation at the target. Multiple sequential illumination and hologram formation/readout steps produce a small spot size at the selected aimpoint. The small spot is maintained at the aimpoint during the duration of an engagement by repeating the above steps.

Claims12

Dependent claims

A laser target acquisition and tracking system with small-spot aimpoint selection and maintenance and compensation for optical distortion comprising:

a) an illuminate laser frequency-locked to a laser master oscillator for directing a first wide-divergence beam of radiation through media toward a target wherein said target reflects a portion of said radiation as a beam or diffuse return;
b) a high speed detector for receiving a portion of said return;
c) a laser local oscillator frequency-locked to said master oscillator and triggered by said detector for generating a short-pulse reference beam where said pulsed reference beam has a variable delay with respect to the leading edge of said return;
d) an electronic radiation detector array for receiving the interference of a portion of said return and said pulsed reference beam for providing detector array signals containing information about said media and a slice of said target selected by the delay and pulse length of said reference beam;
e) a hologram processor responsive to said electronic signals from said radiation detector array to form an electronic hologram pattern;
f) a spatial light modulator responsive to said electronic hologram pattern wherein said spatial light modulator records said hologram as a binary phase pattern;
and
g) a laser for directing a beam of radiation onto said spatial light modulator for providing a phase-conjugate beam being directed to a selected part of said target.

5 more elements

Dependencies are inferred from the claim text.