Infrared holographic projector for thermal masking and decoys

摘要

A holographic structure, system and method project a grey-scale image in a narrow IR spectral band that is related to a broadband thermal signature of an object. The projected grey-scale image, when integrated over the broadband, forms either a decoy that approximates the thermal signature of the object or a mask that obscures the thermal signature of the object. The projected image is a tuned phase recording of a desired far field projection. In different embodiments, the projected image is a “positive” or a “negative” image of the object's thermal signature, a difference image between the thermal signatures of a false object and the object or a camouflage image of random features having approximately the same spatial frequency as the object's thermal signature. The goal being to confuse or fool, even for a short period of time, the warfighting or surveillance system or human observer that uses a broadband IR sensor to acquire and view thermal images of the scene.

主权项

1. An infrared holographic projector comprising:
a grey-scale input image related to a thermal signature of an object, said grey-scale input image having at least three intensity levels; a laser source configured to generate a laser beam in a narrowband including a source wavelength in an infrared spectral range; and an infrared transmissive material having a surface arranged to provide differing amounts of phase-delay to the first laser beam as the beam passes through the material, said surface comprising at least four phase delay layers that correspond to an integer multiple of quarter-wavelengths of total phase delay at a center wavelength, each layer providing a predetermined phase delay at the center wavelength, said surface configured to encode the grey-scale input image, said surface configured to diffract the laser beam at the source wavelength at or near the center wavelength to construct a projected image in the infrared spectrum that forms a decoy that approximates the thermal signature of the object or a mask that obscures the thermal signature of the object.