No abstract

The laser has been regarded as the potential illumination source for the next generation of projectors. However, currently the major issues in applying the laser as an illumination source for projectors are beam shaping and laser speckle. We present a compact solution for both issues by using a vibrating diffractive optical element (DOE). The DOE is designed and fabricated, and it successfully transforms the circular Gaussian laser beam to a low speckle contrast uniform rectangular pattern. Under a vibration frequency of 150 Hz and amplitude of 200 µm, the speckle contrast value is reduced from 67.67% to 13.78%, and the ANSI uniformity is improved from 24.36% to 85.54%. The experimental results demonstrate the feasibility and potential of the proposed scheme, and the proposed method is a feasible approach to the miniaturization of laser projection display illumination systems.

Lasers have been regarded as the potential illumination source for next generation projectors. With the additional feature of coherency, diffractive optical elements (DOEs) become available in the illumination light path. DOEs in laser projection display systems add strong beam-shaping ability, good uniform performance and small size, which makes it is possible to realize efficient and uniform illumination on a spatial light modulator (SLM). Moreover, it is helpful for the simplification and compactness of illumination optics. This paper proposed what we believe is a novel RGB laser projection display illumination system based on a DOE, which used the DOE and optical path compensation system (OPCS) as the beam-shaping and relay system (BSRS), instead of a light pipe and relay lens group in the conventional laser projection display illumination system. We designed the DOE and established the simulation model of the illumination system. The simulation results show that the new illumination system is simple and compact, the illumination uniformity is more than 90%, the illumination efficiency of RGB illumination in BSRS is more than 75%, and the numerical aperture (NA) of the illumination beam is about 0.01.