Scanning micromirror with improved performance and related electronic device
A micromechanical mirror includes a mobile mass carrying a mirror element and provided in a body including semiconductor material. A driving structure is coupled to the mobile mass to cause a scanning movement thereof. The driving structure is configured to generate a combination of a two or more sinusoidal resonant modes in the micromechanical mirror at respective resonant frequencies. This combination approximates a scanning pattern of the mobile mass defined by a linear function which may, in particular, be a triangular shaped function.
1. A micromechanical mirror, comprising:
a mobile mass carrying a mirror element and provided in a body including semiconductor material; and
a driving structure coupled to the mobile mass and configured to cause a scanning movement thereof;
wherein the driving structure is configured to generate a combination of a plurality of sinusoidal resonant modes in the micromechanical mirror at respective plural resonant frequencies, said combination approximating a scanning pattern of said mobile mass defined by a linear function;
wherein the driving structure includes a plurality of distinct driving groups corresponding in number to the plurality of sinusoidal resonant modes;
wherein each of said driving groups includes:
a respective pair of driving arms arranged on opposite sides of the mobile mass with respect to a rotation axis thereof and carrying mobile electrodes;
a respective fixed portion carrying fixed electrodes in a position facing and combfingered with the mobile electrodes; and
elastic elements coupled between the driving arms.
2. The micromechanical mirror according to claim 1 , wherein the linear function is a triangular shaped function.
3. The micromechanical mirror according to claim 1 , wherein the plurality of sinusoidal resonant modes correspond to respective harmonics of a frequency transform of the linear function of said scanning pattern.
4. The micromechanical mirror according to claim 1 , wherein said plurality of sinusoidal resonant modes is equal to two or three, and said plurality of sinusoidal resonant modes correspond to the first two or three harmonics of a series Fourier transform of the linear function of said scanning pattern.
5. The micromechanical mirror according to claim 1 , wherein the elastic elements are of a torsional type.
6. The micromechanical mirror according to claim 1 , wherein the pair driving arms of a first driving group are integrally coupled to the mobile mass; and wherein the pair of driving arms of a second driving group are coupled to anchorages fixed to the body through respective elastic elements.
7. The micromechanical mirror according to claim 1 , wherein the fixed portions carry first contact pads for biasing of the respective fixed electrodes at a respective one of different driving signals.
8. The micromechanical mirror according to claim 7 , wherein the driving signals are sinusoidal signals at the resonant frequencies of the respective resonant modes.
9. The micromechanical mirror according to claim 1 , wherein mechanical parameters of the driving arms and elastic elements of the driving groups define the resonant frequencies of said resonant modes.
10. The micromechanical mirror according to claim 9 , wherein said mechanical parameters comprise: a spring constant of the elastic elements and a moment of inertia of the driving arms.