MEMS resonance control using phase detection

A light projection system, comprising:

• a microelectromechanical (MEMS) mirror configured to operate based on a mirror drive signal and to generate a mirror sense signal as a result of the operation of the MEMS mirror based upon the mirror drive signal;
• a mirror driver configured to generate the mirror drive signal in response to a drive control signal;
• and
• a controller configured to, during each period of the mirror drive signal:
• a) receive the mirror sense signal from the MEMS mirror;
• b) obtain first and second samples of the mirror sense signal at times separated by a half period of the mirror drive signal, the first sample of the mirror sense signal being a first sample of the mirror sense signal taken during a current period of the mirror drive signal, wherein the second sample of the mirror sense signal is a next sample of the mirror sense signal taken after the first sample of the mirror sense signal during the current period of the mirror drive signal, and wherein the second sample of the mirror sense signal is a last sample of the mirror sense signal taken during the current period of the mirror drive signal;
• and
• c) generate the drive control signal such the first and second samples are equal.

A method, comprising steps of:

• a) generating a mirror drive signal in response to a drive control signal and applying the mirror drive signal to a microelectromechanical (MEMS) mirror to drive oscillation of that mirror;
• b) during each period of the mirror drive signal, sampling a mirror sense signal produced by the MEMS mirror twice at times separated by a half period of the mirror drive signal to produce first and second samples, the first sample being sampled when the mirror drive signal is at a first phase and being a first sample of the mirror sense signal taken during a current period of the mirror drive signal, the second sample being sampled when the mirror drive signal is at a second phase that occurs subsequent to the first phase by half a period of the mirror drive signal and being a next sample of the mirror sense signal taken during a current period of the mirror drive signal as well as a last sample of the mirror sense signal taken during the current period of the mirror drive signal;
• c) determining a difference between the first and second samples;
• d) adjusting the drive control signal based upon the difference, if the difference is other than zero;
• and
• e) returning to step a).

A light projection system, comprising:

• a microelectromechanical (MEMS) mirror configured to operate in response to a mirror drive signal and to generate a mirror sense signal as a result of the operation of the MEMS mirror in response to the mirror drive signal;
• a laser configured to emit a laser beam directed at the MEMS mirror so that the MEMS mirror reflects the laser beam across a target surface in a scan pattern;
• a mirror driver configured to generate the mirror drive signal in response to a drive control signal;
• and
• a controller configured to, during each period of the mirror drive signal:
• a) receive the mirror sense signal from the MEMS mirror;
• b) obtain a first sample of the mirror sense signal at a first phase of the mirror drive signal, the first sample of the mirror sense signal being a first sample of the mirror sense signal taken during a current period of the mirror drive signal;
• c) obtain a second sample of the mirror sense signal at a second phase of the mirror drive signal, wherein the first and second phases are separated by a half period of the mirror drive signal, with the second phase occurring after the first phase, wherein the second sample of the mirror sense signal is a next sample of the mirror sense signal taken after the first sample of the mirror sense signal during the current period of the mirror drive signal, and wherein the second sample of the mirror sense signal is a last sample of the mirror sense signal taken during the current period of the mirror drive signal;
• and
• d) generate the drive control signal based upon the first and second samples so as to keep the mirror drive signal separated in phase from the mirror sense signal by a desired amount of phase separation.