Advancing LED and laser projection systems: towards higher lumen output and speckle reduction

Now more than ever before, projection systems are at the frontiers of the visualization industry. Households can easily afford a home theater projection system at a comparable price of an LCD or plasma display, pico projection systems get embedded in head-up displays and cars, but perhaps the business where projection systems are most known for is the entertainment industry. State-of-the-art projection systems create visionary scenes for performance acts and recreate 3D worlds in cinemas. The driving force behind these immersive sensations is the increasing lumen output that projection systems offer. Current lamp-based high-power projection systems, however, are experiencing difficulties projecting immersive 3D content and bright large-area projections because of their limited lumen output. Laser sources are able to overcome this low-lumen obstacle, but the appearance of speckle in the images still remains a hurdle. Limited lumen output is also a point of concern for home theater mid-level power projection systems, as lasers are too expensive for this market segment. In this PhD thesis, state-of-the-art improvements are presented for both home theater projection systems and high-power laser projection systems. Secondary optics for an innovative LED-based light source targeting mid-level power output projection systems are investigated, designed and demonstrated. These secondary optics can significantly enhance the efficacy of the light source and provide a more collimated illumination beam. With respect to laser projection systems, extensive investigations are performed regarding speckle reduction methods and simulating the underlying cause of speckle --i.e. coherence-- inside a classic projection architecture. Besides the typical speckle reduction methods, adjustments to frequently used projection elements that can actively reduce speckle are proposed, investigated and demonstrated. Finally, a speckle measurement procedure, matched to human visual perception is introduced and investigated. This procedure was used in the study of a speckle threshold using large-scale subjective perception tests, both in the case of still and moving images.