1. A sensor comprising:
a plurality of laser transmitter units, wherein each of the plurality of laser transmitter units is configured to transmit
a light beam having a plurality of wavelengths;
a photodetector; and
an optical system coupled to the plurality of laser transmitter units and the photodetector;
wherein the optical system directs the light beam from each of the laser transmitter units onto a same illuminated spot on
a probed surface; and
wherein the optical system collects light from the same illuminated spot and directs the light to the photodetector.