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The uniformization of Gaussian beam intensity is necessary in many applications. In active night-vision, monitoring targets especially requires this. IR semiconductor laser is widely used in the area because of its low power-consumption and small size. But the effects of the product are restrained due to system output Gaussian beam of ununiform intensity. The essay discusses a former system design and then gives an improved experimental scheme with some exciting results. The previous structure was as follows. High power SQW-LD beam was coupled to a plastic optical fiber (POF) directly, and then output through a lens. With its angle varied, targets ranged from 60 to 100 meters can be monitored. But unfortunately there were interference speckles folded on the target. An experimental system based on the thoughts of fiber transmission and complex filter was designed to improve the distribution of Gaussian beam intensity, with the result that the relatively well-distributed beam was got. Laser wavefront propagated through a very small pinhole whose diameter was 20 micrometers or so. The pinhole acted as an amplitude filter. Then the beam was coupled directly into a multi-mode quartz fiber whose core/cladding layer diameter parameter was 50/125micrometers . It conveyed laser beam about 200 mm. At the end of the fiber, several phase plates stood. Laser beam transmitted through the fiber was then phase-filtered and at last beam-expanded by a lens to illuminate the target. The more plates you used, the more uniform the illuminated picture was on condition the beam intensity was so strong that the CCD device could respond to.
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