Adaptive Micromirror Array

The adaptive optical system real-time adjusts wave-front distortion through the mirror's deformation to acquire sharp image, the most complicated and representational part is the deformable mirror. As high cost and difficulty in control, the deformation mirror fabricated in conventional way can't satisfy with current requirement. In micro-optical adaptive system, the deformable mirror, fabricated with the micro- machining process, obviously reduces the costs, enhances the efficiency, and at the same time compatible with the IC process, fits mass production. With the development of Micro-Opto-Electro-Mechanical System (MOMES), it has been possible to fabricate deformable micro-mirror which is measured in micrometer, and accordingly this will impulse the development of micro-optical adaptive system.A novel adjustable focal length optical adaptive micro-mirror array is presented. Based on bi-metal effect, the deformable micro-mirror array, fabricated with micro-machining process, has the advantage of low driving voltage, high driving strength. We designed an Active Mirror Device (AMD), and mainly did some researches on micro-machining process, improved the performance of the AMD though changing processing condition. Micro-machining processes such as thermal oxygenation, photolithography, HF isotropic etching, KOH anisotropic etching, sputtering, and fabrication of electrodes are experimented. An systemic research was did on KOH wet etching, influences of concentration and temperature to etching rate and roughness are discussed, roughness in deep-etching is also discussed. Thus, we have a general trend, and a brief analysis of its causes, also we got the best etching condition.A 4×4 micro-mirror array has been completed. The whole mirror has the area of 30×30 mm~2, with each unit of 1.5×1.5 mm~2, the thickness of silicon is 50μm and Aluminum film 100 nm, roughness of the mirror is 20A, deformable mirror area covers 41% of the whole mirror area. Performance of adjustable focal length micro-mirror array is tested, using laser wave-front interferometer. Experiment results demonstrate that, the micro-mirror array can produce unidirectional continuous deformation with the maximum deformation of 7.75μm and a lag of 9.645%, and has fine linearity . It can work at 0～11V with an adjustable focal length ranging from∞to 30mm.