Study on resonant frequency for a novel MEMS micro scanning mirror

Based on the micro-opto-electro-mechanical systems (MOEMS) technology, a new resonant micro scanning mirror using silicion-on-insulator (SOI) process is designed and fabricated. Its basic operational principle and structural characterizations are briefly introduced. The resonant frequency considered to be its most important mechanical parameter is theoretically computed according to the two designed structural dimensions and numerically simulated by combining the finite element simulation tool of ANSYS. A simple but efficient optical system is set up for practically measuring their scanning angle of the designed micro scanning mirror. According to the characteristic of hysteretic frequency responses of parametric excitation of the designed micro scanning mirror, the resonant frequency is measured. To verify the accuracy of the testing results, the resonant frequency is achieved by the laser Doppler vibrometer (LDV). With the driving voltage of 10 V, the mechanical scanning angles for the square and circular scanning mirror reach to about 6° and 5° respectively while the drive frequencies are 556 Hz and 596 Hz. Furthermore, the resonant frequency approximately reaches to 300 Hz and 277 Hz. All the derived results are comparised and very error cause is analyzed.