Figure 1.

A schematic illustration of the high definition, high frame rate (HDHF) Lissajous MEMS mirror. A conventional raster MEMS mirror provides two-dimensional (2D) scanning with a ratio of two frequencies of 1:N and a torsional micromirror usually requires a flexible micro-spring. Unlike raster scanning MEMS mirrors, conventional Lissajous MEMS mirrors have high mechanical stability. Conventional Lissajous mirrors also have a high Q factor, which derives a substantial change of the scanning amplitude depending on the scanning frequency. In contrast, the HDHF Lissajous MEMS mirror features an inner mirror with a low Q-factor, which allowed a broad selection range of scanning frequencies. The selection of scanning frequencies at pseudo-resonance with a high greatest common divisor (GCD) and a high total lobe number (N, ($f_x$ + $f_y$)/GCD), which is larger than the minimum total lobe number ($N_{min}$) for the targeted FF, enabled HDHF Lissajous scanning. Since the designed MEMS mirror is for 2D laser scanning, biaxial scanning frequencies had to be selected. Note that $f_x$ and $f_y$ infer the resonant frequencies of the inner mirror and the frame mirror, respectively. In addition, biaxial scanning frequencies are defined as $f_x$’ and $f_y$’, which infer the selected freque-ncies of the inner mirror and frame mirror, respectively, determined by the frequency selection rule.