Design, Modeling, and Characterization of a Microelectromechanical Diffuser Device for Laser Speckle Reduction

Speckle noise is a major obstacle for the application of laser light sources in projection displays and illumination. In this paper, a method for speckle reduction using a Micro-Electro-Mechanical Systems (MEMS) diffuser device is presented. The MEMS device consists of a random reflective pattern on the top surface of a moving mass that is vibrated in-plane by an electrostatic push-pull comb drive. The harmonic in-plane motion of the MEMS diffuser creates time-varying speckle patterns that are averaged by the camera or the eye, thus reducing speckle noise. The device is fabricated using Silicon-On-Insulator (SOI) technology. The measured device shows good agreement with analytical calculation and simulation. Using a red He-Ne laser, speckle contrast is measured both for free space geometry and for light pipe geometry. Speckle contrast reduction up to 43.08% for the free space geometry and 26.8% for the light pipe geometry is achieved.