Patent ID: 9229024
Filing Date: 2016-01-05
CPC Classification: B60T,G01C,G01P,G01S

Claim Text:
1. A method of adjusting a self-mixing laser sensor for measuring a velocity of a vehicle moving relative to a reference surface, the method comprising the acts of: determining a frequency of self-mixing intensity oscillations caused by Doppler-induced phase shift of laser light reflected back from the reference surface and re-entering a cavity of at least one laser; calculating a velocity from said frequency of the self-mixing intensity oscillations; determining an orientation of the self-mixing laser sensor in relation to the reference surface and a predetermined direction of movement of the vehicle along said predetermined direction of movement using at least a first laser beam of said self-mixing laser sensor, said act of determining the orientation of the self-mixing laser sensor comprising the acts of determining whether a direction of movement of the vehicle coincides with the predetermined direction of movement, obtaining velocity data measured by the self-mixing laser sensor for the movement of said vehicle along said predetermined direction of movement, and calculating a transformation based on said velocity data for the movement of said vehicle along said predetermined direction of movement; and adjusting the velocity data determined by the self-mixing laser sensor based on the determined orientation of the self-mixing laser sensor, said act of adjusting velocity data comprising applying said transformation to the measured velocity data, wherein the at least one laser comprises three lasers for providing at least three laser beams, and wherein the method further comprises the acts of: determining the velocity along the predetermined direction from said self-mixing intensity oscillations; detecting phase jumps or minima of a self-mixing Doppler induced intensity oscillation of at least one of at least three laser beams at interfaces of speckle induced intensity oscillations; and correcting a deviation of a signal derived from a frequency of the Doppler induced intensity oscillation at the interfaces of speckle induced intensity oscillations, the deviation resulting from the Doppler-induced phase shift.