Thermoelectrically controlled varifocal micromirror for near aberration free imaging

A close-loop-controlled miniature Peltier element was used to vary the temperature of a 1.2 mm diameter silicon-gold bimorph varifocal micromirror (VFM), thereby changing its radius of curvature due to differential thermal expansion of the two materials. By varying the VFM temperature from 10°C to 100°C, the radius of curvature (ROC) of the micromirror was measured to vary from 19.2mm to 30.9mm. The Zernike coefficients over this operational range were analysed to be less than a few micrometres. An imaging system utilising the VFM was assembled, and examples of the near aberration-free images obtained are presented.