US Patent 10327069 Laser microphone utilizing speckles noise reduction

A system includes a laser microphone or laser-based microphone or optical microphone. The laser microphone includes a laser transmitter to transmit an outgoing laser beam towards a face of a human speaker. The laser transmitter acts also as a self-mix interferometry unit that receives the optical feedback signal reflected from the face of the human speaker, and generates an optical self-mix signal by self-mixing interferometry of the laser power and the received optical feedback signal; and a speckles noise reducer to reduce speckles noise and to increase a bandwidth of the optical self-mix signal. The speckles noise reducer optionally includes a vibration unit or displacement unit, to cause vibrations or displacement of one or more mirrors or optics elements of the laser microphone, to thereby reduce speckles noise. The speckles noise reducer optionally includes a dynamic laser modulation modifier unit, to dynamically modify modulation properties of a laser modulator associated with the laser transmitter; optionally by modifying an operating temperature of the laser. Optionally, modifications are performed based on a timing scheme, or based on a pseudo-random scheme, or based on a calibration process that selects an advantageous modification scheme. Optionally, the system detects self-mix signal magnitude or bandwidth or quality, and activates the speckles noise reduction mechanism if the self-mix signal appears to be weak or low-quality.