Research on Multi-wavelength and Multi-beam Illumination for Improving Object Illumination Uniformity

The imaging and tracking to the far dim objects in the air are usually difficult for detecting system to get their clear images and accurate positions, due to the objects neither emitting light nor reflecting sunlight. Using active laser illumination technology, the target will be illuminated and the echo intensity of target can be increased. The laser intensity spatial distribution on the target plane fluctuates usually remarkably due to the atmospheric turbulence and other causes, which will decrease image resolution and tracking accuracy in optical system. In this paper, we presented a method of using illumination with the supercontinuum spectrum laser beam combination to improve the effect of target illumination uniformity. As the atmosphere transmittance ratios differs with wavelength, we set up a multi-wavelength and multi-beam target illumination simulation system to represent the supercontinuum spectrum laser illumination effect. As the previous simulation results and the experimental results, which both reflect an improving effect of illumination uniformity significantly by increasing of the beam number. The illumination uniformity of single beam with multi-wavelength spectrum components was analyzed, and the simulation results of one single beam, three beams and six beams with 9 wavelength spectrum were compared, which showed that the illumination uniformity in target plane was improved with both the number of wavelength spectrum components and the number of beams increasing. It showed that multi-spectral multi-beam illumination had great advantages in improving illumination uniformity and the supercontinuum laser can be a good active illumination source.