Mixed Sources Illumination And Laser Speckle Suppression In Micro Projection System

Projection display is an important part of display industry. As people require more and more on performance and portability of display equipments, micro projection system has become a hot spot in electronical consumption research since semiconductor technology greatly developed.Source choosing in micro projection system is researched. Advantages and disadvantages of popular sources are analyzed, specific demands on micro projection system source are discussed, the conclusion that these specific demands can not all be satisfied by one kind source is made.1931 CIE-RGB system and some concepts of photometry and colorimetry are introduced, the luminous flux demands of tricolor sources in micro projection system are conducted. A mixture sources illumination based on green DPL, red LD and blue LED is proposed, more analysis is made to indicate its feasibility.Laser speckle, the most serious problem when laser is used as the illumination source of micro projection system, is researched. Statistical properties of speckel and principles of speckle suppression are discussed, shortcomings of conventional speckle suppression methods are analyzed, the conclusion that the energy efficiency and speckle suppression are incompatible in conventional speckle suppression is made. A novel method of speckle suppression with a rotating light pipe is proposed to overcome the problem, a series simulation in computer indicate that the novel method is effective in speckle suppression, energy preservation and polarization maintaining.Relay lenses are designed due to different properties of green DPL, red LD and blue LED, simulation results show that by passing these relay lenses, the uniformity of illumination beams is> 83% and diffuse angle< 7.2°. Optical components are made according to the design, a experimental system is built and a series experiments are performed to validate the system is effective in speckle suppression, energy preservation and uniform illumination. Projection images acquired from the experiments has speckle contrasts< 5% and uniformity> 80%. Energy efficiency of the system is> 15%.Developing trend of micro projection system is discussed. Mass production of DLP and LCoS chips, improvement of LED performance and cost reduction of laser sources are main approaches of micro projection developing. Pico projector will be the major developing trend of micro projection.