Microsystem scanning mirrors are known e.g. from U.S. Pat. No. 7,295,726 B1. Such microsystem scanning mirrors are often operated resonantly, with the result that the tilt angle oscillates at the resonant frequency of the scanning mirror and thus describes sinusoidal patterns or Lissajous patterns. In these cases, it is often sufficient if only the zero-crossing is detected. In the case of electrostatic comb-drives, this is primarily carried out by measuring the maximum capacity of the comb-drives during the oscillation. Piezoresistive and inductive measurements are also common.
Although, in the case of a quasistatic positioning of the scanning mirror, the capacities can still be measured in the case of comb-drives, it has been shown that this is too imprecise and also often does not correlate precisely with the tilt angle of the scanning mirror. It is not possible to measure the piezoelectric resistance of the solid state joints for moving the scanning mirror, because the solid state joints are too thin in the case of quasistatic mirrors.
USPTO Backgrounds
USPTO Backgrounds