Multichannel optical power meter using a synchronous scanner
AssigneeCalient Technologies, Inc.
InventorMichael Inbar
Life of this patent
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Abstract
Optical scanning systems and methods of controlling a resonant scanning mirror are disclosed. A rotatable mirror may oscillate about a rotation axis in response to a drive signal. A reference source may provide a reference light beam directed to the rotatable mirror. A reference detector may be disposed to receive the reference light beam reflected from the rotatable mirror twice during each oscillation of the rotatable mirror. A controller may set both an amplitude and a frequency of the drive signal based on an output of the reference detector.
Claims16
An optical scanning system, comprising:
- a scanning mirror that oscillates about a rotation axis in response to a drive signal;
- a reference source to provide a reference light beam directed to the scanning mirror;
- a reference detector disposed to receive the reference light beam reflected from the scanning mirror twice during each oscillation of the scanning mirror, the reference detector outputting two pulses during each oscillation of the scanning mirror, a time interval between the two pulses less than one-half of an oscillation period of the scanning mirror;
- and
- a controller that sets both an amplitude and a frequency of the drive signal based on an output of the reference detector, wherein the controller further comprises:
- a windowed integrator to compute an integral of the drive signal over the oscillation period exclusive of the time interval between the peaks of the two pulses;
- a second subtractor to determine a difference between a second predetermined value and an output of the windowed integrator at an end of each integration period;
- a second integrator to integrate the output of the second subtractor,
- a direct digital synthesizer configured to output a square wave, wherein a frequency of the square wave is set by an output of the second integrator.
A method of controlling a resonant scanning mirror that oscillates about a rotation axis in response to a drive signal, comprising:
- directing a reference light beam directed to the resonant scanning mirror;
- a reference detector receiving the reference light beam reflected from the resonant scanning mirror twice during each oscillation of the resonant scanning mirror, the reference detector outputting two pulses during each oscillation of the scanning mirror, a time interval between the two pulses less than one-half of an oscillation period of the scanning mirror;
- and
- setting both an amplitude and a frequency of the drive signal based on an output of the reference detector, wherein setting the frequency of the drive signal comprises:
- performing a windowed integration of the drive signal over the oscillation period exclusive of the time interval between the peaks of the two pulses;
- substracting a result of the windowed integration at an end of each integration period from a second predetermined value to provide a phase error;
- integrating the phase error;
- and
- synthesizing a square wave, wherein a frequency of the square wave is set by the integrated phase error.
Dependencies are inferred from the claim text.