Laser range finding using the self-mixing effect in a vertical-cavity surface emitting laser

In this paper we report on a laser range finding system built using the self-mixing effect in a vertical-cavity surface-emitting laser (VCSEL). The distance to the target in these range finders is usually calculated by determining the time interval between the peaks in the resulting power fluctuations that are produced by the self-mixing effect. In this study we propose the use of a method that utilises the fast Fourier transform (FFT) that proves to have better performance than the traditional peak spacing methods used by other researchers. A range finding system has been built using a VCSEL and the FFT to measure a range of distances from 20 cm to 1 m with a maximum error of 1.5% and a resolution of 5 mm. This is the first time to our knowledge that such a range finding system has been built with a VCSEL.