Obstacle detection and spectral discrimination using multi-wavelength motionless wide angle laser scanning.

Static laser scanning over a wide angle is demonstrated by ranging to 20 laser beams generated by a novel cylindrical quasi-cavity waveguide, using laser triangulation. Baseline distances and outgoing angles unique to each laser beam are calculated by modelling the triangulation arrangement using a system of linear equations and plotting principal rays. The quasi-cavity waveguide, imaging lens and focal plane are also plotted. The system is calibrated by finding optimal values for uncertain instrumental parameters using constrained non-linear optimization. Distances calculated over 5m indoors result in accuracies above 93%. Discrete laser spectroscopy using 640nm and 785nm laser diodes is also demonstrated. Both injected laser beams follow the same optical path through the quasi-cavity waveguide, enabling spectral measurements to be made from the same point on an object for both wavelengths. The reflected red and infrared laser light is digitally recorded by a CCD imager and differences in reflected intensity enable discrimination between various natural objects. This provides more complete information about the perturbing object, including its 3D coordinates as well as limited identification of its surface material.