Coherence Collapse - Speckle Reduction at the Laser Source
Agency / Branch:
DOD / USAF
Laser projection systems deliver the highest resolution, contrast ratios, color purity, and screen uniformity as compared to other display technologies used in flight simulation but suffer from an image artifact called speckle that manifests as random variations in the image intensity resulting from interference of many projected and scattered coherent laser light waves. Contractor proposes a speckle reduction technique based on operating three (Red, Green, Blue) projector lasers in the state of coherence collapse to achieve speckle contrast reduction to below 5%. This method will significantly reduce real time imaging system speckle noise while maintaining overall image quality and spatial and temporal display resolution. In phase I, the speckle reduction due to spectral broadening and the impact of increased high frequency noise will be evaluated for display applications. The effect of coherence collapse state in destroying the fixed relative phase-relationship between modes of a multi-frequency laser will be studied. Research goals are to demonstrate the feasibility of coherence collapse as a speckle reduction method that can achieve less than 5% speckle contrast and to propose a design that incorporates coherence collapse inside Microvision pico projector engine, as well as existing and future laser projectors in flight simulators and commercial applications. BENEFIT: The research conducted during this phase will enable significant reduction or elimination of optical speckle in real-time coherent imaging systems. Current laser projection systems used by the Air Force for flight simulation suffer from significant image speckle which reduces image detail and overall realism. The solution proposed will reduce the speckle phenomena while maintaining the other advantages of laser imaging systems. Potential commercial applications of the research and development include introduction into near-term see-through eyewear product for military and consumer markets and full-color see-through Head-Up Displays for airborne and ground (combat and tactical) vehicles.
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