Optical projection display systems integrated with three-color-mixing waveguides and grating-light-valve devices

An integrated optical projection display technique utilizing three-color-mixing waveguides and grating-light-valve devices is demonstrated. This new projection display system comprises an optical lens, a microscanner, a grating light valve, and a 3x1 planar waveguide device. The planar waveguide device is fabricated using a SU-8 negative photoresist process, which is suitable material for rapid prototyping of integrated optical circuits. It works as a three-color-mixer and is successfully used for color image generation. The intensity of color for each pixel in the display picture is tuned by groups of movable ribbons comprising a grating light valve and image generating diffraction gratings. This study also demonstrates a surface-micromachined optical scanner using four stress-actuated polysilicon plates to raise a horizontal mirror. The electrostatically driven mirror can be used for scanning projection display applications. Experimental data show that the optical scanner has a mirror scanning angle up to +/-15(o) using an operating voltage of 25 V. A sub-millisecond switching time (<900 mus) and an optical insertion loss of 0.85 dB is achieved for multi-mode waveguides. The development of the proposed integrated optical system could be promising for an image generation system.