Scanning mirror control

A method comprising:

• characterizing a scanning mirror by exciting the scanning mirror at different frequencies and measuring a response;
• determining a weighting array proportional to an inverse of the scanning mirror response;
• and
• using the weighting array to weight learning rates of harmonic drive coefficients in a feedback loop, the harmonic drive coefficients to produce angular displacement of the scanning mirror.

A computer-readable medium having instructions stored thereon that when accessed result in a computer performing:

• receiving time domain data describing angular movement of a scanning mirror in a slow-scan direction;
• performing a fast Fourier transform on the time domain data to produce return harmonic coefficients;
• comparing the return harmonic coefficients with harmonic coefficient targets to determine errors;
• modifying a plurality of drive coefficients by differing amounts to reduce the errors;
• and
• performing an inverse fast Fourier transform on the drive coefficients to produce a drive waveform to drive the scanning mirror in the slow-scan direction.

An apparatus comprising:

• a scanning mirror having a fast-scan axis and a slow-scan axis, the slow-scan axis having a position detector;
• an outer control loop that operates in the frequency domain to determine harmonic coefficients of a drive signal in response to position information received from the position detector;
• and
• an inner control loop that operates in the time domain to compensate for a scanning mirror resonant vibration mode at a frequency within a frequency band occupied by the harmonic coefficients of the drive signal.

A mobile device comprising:

• a communications transceiver;
• a scanning mirror;
• and
• a slow-scan scanning mirror control system having an outer loop operating in the frequency domain and an inner loop operating in the time domain.