System-level synchronization of microelectromechanical system (MEMS) mirrors

1 . An oscillator system, comprising:

a first oscillator structure configured to oscillate about a first axis;

a first driver configured to generate a first driving signal to drive an oscillation of the first oscillator structure about the first axis with a first target oscillation frequency, wherein the first driver includes a first phase detector configured to generate a first phase error signal representative of a first phase error between a measured oscillation of the first oscillator structure about the first axis and an expected oscillation having a first target oscillation phase;

a first frequency control loop configured to regulate a frequency of the oscillation of the first oscillator structure about the first axis; and

a first phase control loop comprising a first phase controller configured to receive the first phase error signal and generate a first actuation value based on the first phase error signal, wherein the first phase controller is configured to adjust the first actuation value based on the first phase error signal to adjust a first actuation phase of the first oscillator structure about the first axis to minimize the first phase error,

wherein the first driver is configured to generate the first driving signal based on the first actuation value, and

wherein the first frequency control loop and the first phase control loop are independent control loops with no overlap.

2 . The oscillator system of claim 1 , wherein the first phase controller is a first loop filter configured to generate the first actuation value based on the first phase error signal, and transmit the first actuation value to the first driver.

3 . The oscillator system of claim 1 , wherein:

the first driving signal comprises an ON duration and an OFF duration that define a first duty cycle of the first driving signal, and

the first actuation value controls at least one of the ON duration or the OFF duration for controlling the first duty cycle of the first driving signal.

4 . An oscillator system, comprising:

a first oscillator structure configured to oscillate about a first axis;

a first driver configured to generate a first driving signal to drive an oscillation of the first oscillator structure about the first axis with a first oscillation frequency, wherein the first driver includes a first phase detector configured to generate a first phase error signal representative of a first phase error between a measured oscillation of the first oscillator structure about the first axis and an expected oscillation having a first target oscillation phase; and

a first phase controller configured to receive the first phase error signal and generate a first actuation value based on the first phase error signal, wherein the first phase controller is configured to adjust the first actuation value based on the first phase error signal to adjust a first actuation phase of the first oscillator structure about the first axis to minimize the first phase error,

wherein the first driver is configured to generate the first driving signal based on the first actuation value,

wherein the first driving signal comprises an ON duration and an OFF duration that define a first duty cycle of the first driving signal, a first signal level set for the ON duration, and a second signal level set for the OFF duration, and

wherein the first actuation value controls the first signal level or the second signal level of the first driving signal.

5 . The oscillator system of claim 1 , wherein the first phase controller is configured to adjust the first actuation value based on the first phase error signal to adjust the first actuation phase of the first oscillator structure independent of the first target oscillation frequency such that the frequency of the oscillation is not affected by an adjustment to the first actuation phase.

6 . The oscillator system of claim 1 , wherein the first driver is configured to receive the first actuation value and control an actuation of the first oscillator structure based on the first actuation value such that a phase of the oscillation of the first oscillator structure follows the first target oscillation phase independent of the frequency of the oscillation of the first oscillator structure.

7 . The oscillator system of claim 1 , wherein the first driver is configured to detect a zero-crossing time of the first oscillator structure, and the first phase detector is configured calculate a difference between the detected zero-crossing time and a reference zero-crossing time as the first phase error.

8 . The oscillator system of claim 1 , wherein the first driver is configured to generate a first position signal having a signal frequency corresponding to an actual frequency of the oscillation of the first oscillator structure about the first axis, wherein the first frequency control loop comprises:

a frequency controller configured to receive the first position signal and change an actuation frequency of the first oscillator structure with respect to the first axis based on the signal frequency of the first position signal such that the actual frequency follows the first target oscillation frequency,

wherein the first driver is configured to generate the first driving signal based on the actuation frequency.

9 . The oscillator system of claim 8 , wherein the frequency controller comprises:

a phase frequency detector configured to receive the first position signal and a reference signal having the first target oscillation frequency and generate a first frequency error signal as a difference between the signal frequency of the first position signal and the first target oscillation frequency of the reference signal; and

a loop filter configured to receive the first frequency error signal and generate a control signal based on the first frequency error signal,

wherein the first driver is configured to receive the first frequency error signal and change the actuation frequency to match the first target oscillation frequency.

10 . The oscillator system of claim 8 , wherein the first driver is configured to receive a first frequency error signal representative of a difference between the signal frequency of the first position signal and the first target oscillation frequency and generate the first driving signal based on the first frequency error signal such that a frequency of the first driving signal matches the first target oscillation frequency.

11 . The oscillator system of claim 1 , wherein:

the first oscillator structure is configured to oscillate about a second axis, wherein the oscillator system further comprises:

a second driver configured to generate a second driving signal to drive an oscillation of the first oscillator structure about the second axis with a second target oscillation frequency, wherein the second driver includes a second phase detector configured to generate a second phase error signal representative of a second phase error between a measured oscillation of the first oscillator structure about the second axis and an expected oscillation having a second target oscillation phase;

a second frequency control loop configured to regulate a frequency of the oscillation of the first oscillator structure about the second axis; and

a second phase control loop comprising a second phase controller configured to receive the second phase error signal and generate a second actuation value based on the second phase error signal, wherein the second phase controller is configured to adjust the second actuation value based on the second phase error signal to adjust a second actuation phase of the first oscillator structure about the second axis to minimize the second phase error,

wherein the second driver is configured to generate the second driving signal based on the second actuation value, and

wherein the second frequency control loop and the second phase control loop are independent control loops with no overlap.

12 . The oscillator system of claim 11 , wherein the second driver is configured to generate a second position signal having a signal frequency corresponding to an actual frequency of the oscillation of the first oscillator structure about the second axis, wherein the second frequency control loop comprises:

a frequency controller configured to receive the second position signal and change an actuation frequency of the first oscillator structure with respect to the second axis based on the signal frequency of the second position signal such that the actual frequency follows the second target oscillation frequency,

wherein second driver is configured to generate the second driving signal based on the actuation frequency.

13 . The oscillator system of claim 1 , further comprising:

a second oscillator structure configured to oscillate about a second axis;

a second driver configured to generate a second driving signal to drive an oscillation of the second oscillator structure about the second axis with a second target oscillation frequency, wherein the second driver includes a second phase detector configured to generate a second phase error signal representative of a second phase error between a measured oscillation of the second oscillator structure about the second axis and an expected oscillation having a second target oscillation phase;

a second frequency control loop configured to regulate a frequency of the oscillation of the second oscillator structure about the second axis; and

a second phase control loop comprising a second phase controller configured to receive the second phase error signal and generate a second actuation value based on the second phase error signal, wherein the second phase controller is configured to adjust the second actuation value based on the second phase error signal to adjust a second actuation phase of the second oscillator structure about the second axis to minimize the second phase error,

wherein the second driver is configured to generate the second driving signal based on the second actuation value, and

wherein the second frequency control loop and the second phase control loop are independent control loops with no overlap.

14 . The oscillator system of claim 13 , wherein the second driver is configured to generate a second position signal having a signal frequency corresponding to an actual frequency of the oscillation of the second oscillator structure about the second axis, wherein the second frequency control loop comprises:

a frequency controller configured to receive the second position signal and change an actuation frequency of the second oscillator structure with respect to the second axis based on the signal frequency of the second position signal such that the actual frequency follows the second target oscillation frequency,

wherein second driver is configured to generate the second driving signal based on the actuation frequency.

15 . The oscillator system of claim 13 , wherein:

the first driver is configured to generate a first position signal having a signal frequency corresponding to an actual frequency of the oscillation of the first oscillator structure about the first axis,

the second driver is configured to generate a second position signal having a signal frequency corresponding to an actual frequency of the oscillation of the second oscillator structure about the second axis,

the first frequency control loop comprises a first frequency controller configured to receive the first position signal and a first reference signal having the first target oscillation frequency, and change an actuation frequency of the first oscillator structure with respect to the first axis based on a first difference between the signal frequency of the first position signal and the first target oscillation frequency of the first reference signal such that the actual frequency of the oscillation of the first oscillator structure follows the first target oscillation frequency, and

the second frequency control loop comprises a second frequency controller configured to receive the second position signal and a second reference signal having the second target oscillation frequency, and change an actuation frequency of the second oscillator structure with respect to the second axis based on a second difference between the signal frequency of the second position signal and the second target oscillation frequency of the second reference signal such that the actual frequency of the oscillation of the second oscillator structure follows the second target oscillation frequency.

16 . The oscillator system of claim 15 , further comprising:

a phase detector configured to receive the first position signal and the second position signal and measure a phase difference therebetween; and

a Lissajous frame start detector configured to receive the measured phase difference and determine a start of a Lissajous frame based on the measured phase difference.

17 . The oscillator system of claim 16 , wherein the phase detector is arranged on a start control path that is separate from the first phase control loop and the second phase control loop.

18 . The oscillator system of claim 15 , further comprising:

a clock source comprising an oscillator configured to generate a clock signal, where the clock source is configured to generate the first reference signal having the first target oscillation frequency and the second reference signal having the second target oscillation frequency from the clock signal,

wherein the first target oscillation frequency and the second target oscillation frequency are different and have a fixed frequency difference therebetween.

19 . The oscillator system of claim 18 , further comprising:

a phase detector configured to receive the first reference signal and the second reference signal and measure a phase difference therebetween; and

a Lissajous frame start detector configured to receive the measured phase difference and determine a start of a Lissajous frame based on the measured phase difference.

20 . The oscillator system of claim 18 , wherein the clock source includes a fractional n-divider configured to divide the clock signal by a first integer to generate divided clock signal, a first divider that divides the divided clock signal by a second integer to generate the first reference signal having the first target oscillation frequency, and a second divider that divides the divided clock signal by a third integer to generate the second reference signal having the second target oscillation frequency.

21 . The oscillator system of claim 18 , wherein the clock source includes a plurality of dividers configured to generate, from the clock signal, the first reference signal and the second reference signal that have a defined fractional relationship.

22 . An oscillator system, comprising:

a first oscillator structure configured to oscillate about a first axis;

a first driver configured to generate a first driving signal to drive an oscillation of the first oscillator structure about the first axis with a first target oscillation phase and a first target oscillation frequency, wherein the first driver is configured to generate a first position signal having a signal frequency corresponding to an actual frequency of the oscillation of the first oscillator structure about the first axis;

a phase control loop configured to regulate a phase of the oscillation of the first oscillator structure about the first axis; and

a frequency control loop comprising a first frequency controller configured to receive the first position signal and change a first actuation frequency of the first oscillator structure with respect to the first axis based on the signal frequency of the first position signal such that the actual frequency follows the first target oscillation frequency,

wherein the first driver is configured to generate the first driving signal based on the first actuation frequency, and

wherein the frequency control loop and the phase control loop are independent control loops with no overlap.

23 . The oscillator system of claim 22 , wherein the first driver is configured to receive a first measurement signal representative of an entire angular trajectory traversed by the first oscillator structure throughout its oscillation, detect first zero-crossing events of the first oscillator structure at which a value of the first measurement signal is detected to be equal to first predefined value that corresponds to a zero displacement angle of the first oscillator structure with respect to the first axis, and generate the first position signal that indicates each of the detected first zero-crossing events with a rising signal transition or a falling signal transition.

24 . The oscillator system of claim 22 , further comprising:

a second oscillator structure configured to oscillate about a second axis;

a second driver configured to generate a second driving signal to drive an oscillation of the second oscillator structure about the second axis with a second target oscillation phase and a second target oscillation frequency, wherein the second driver is configured to generate a second position signal having a signal frequency corresponding to an actual frequency of the oscillation of the second oscillator structure about the second axis; and

a second frequency controller configured to receive the second position signal and a second reference signal having the second target oscillation frequency, and change a second actuation frequency of the second oscillator structure with respect to the second axis based on a second difference between the signal frequency of the second position signal and the second target oscillation frequency of the second reference signal such that the actual frequency of the oscillation of the second oscillator structure follows the second target oscillation frequency,

wherein the second driver is configured to generate the second driving signal based on the second actuation frequency.

25 . The oscillator system of claim 24 , further comprising:

a phase detector configured to receive the first position signal and the second position signal and measure a phase difference therebetween; and

a Lissajous frame start detector configured to receive the measured phase difference and determine a start of a Lissajous frame based on the measured phase difference.

26 . The oscillator system of claim 24 , further comprising:

a clock source comprising an oscillator configured to generate a clock signal, where the clock source is configured to generate a first reference signal having the first target oscillation frequency and the second reference signal having the second target oscillation frequency from the clock signal,

wherein the first target oscillation frequency and the second target oscillation frequency are different and have a fixed frequency difference therebetween.

27 . The oscillator system of claim 26 , further comprising:

a phase detector configured to receive the first reference signal and the second reference signal and measure a phase difference therebetween; and

a Lissajous frame start detector configured to receive the measured phase difference and determine a start of a Lissajous frame based on the measured phase difference.