The photoelectric parameters degradation of Si-based PIN photodiodes irradiated by 1064 nm millisecond Nd:YAG laser has been measured. The samples were the commercial silicon PIN photodiodes BPW34 with plastic package. The applied laser fluence levels range from 20J/cm2 to 1400J/cm2. Surface damage morphology, dark current and sensitivity were investigated for the irradiated photodiodes. It has been shown that the dark current was the first and the most sensitive degradation parameter, and we believe that the dislocation introduced by the tangential component of thermal stress in the [111] and [110] direction was the main reason. The sensitivity decrease until the dark current reach to μA magnitude and the surface have melted seriously, the finite element method was used to calculation the dopant redistribution process. It shows that the degradation of sensitivity depends greatly on the process under various applied laser fluencies.
This paper proposes a novel sub-pixel locating algorithm improving the performance of time-consuming template matching based on
the Normalized Cross Correlation (NCC), which is widely applied in locating the surface mounting components of PCB (Printed
Circuit Board). Based on the NCC, the proposed algorithm improves the performance significantly by modifying the NCC function,
and adopting coarse-to-fine search. For the locating position with sub-pixel precision, according to the condition of the correlation
peak, the outline of the longitudinal section along the correlation peak is obtained by cubic spline interpolation. The longitudinal
section is executed along different directions to acquire different peaks. The optimum position can be found at the point where the sum
of distances from it to all other points is the least. And the optimum position is also the position of the surface mounting components
with sub-pixel precision. Experimental results demonstrate that the proposed algorithm can not only reduce computational complexity
significantly, but also increase the locating accuracy effectively.
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