Practical accurate optical ranging based on polarization self modulation of a vertical-cavity surface-emitting laser diode

A self-mixing type range finder is proposed using the polarization self modulation phenomenon of a vertical-cavity surface-emitting laser diode, in which the polarization mode switches between two inherent modes of the laser diode. The length to be measured is determined from the switching frequency, the accuracy of which is quite excellent with a relative error of less than 10 ppm. Experimental results prove that the present method is feasible as a practical and highly accurate ranging technique.