Detection of central positions of noisy rounded square function using modified Haar wavelet transform and Haar-Gaussian wavelet transform

We propose and demonstrate new wavelet transforms, the modified Haar wavele t transform and Haar-Gaussian wavelet transform, for the detection of centr al positions of a noisy rounded square function. The advantage is the immun ity of the wavelet transform to random noise. The alternative technique bas ed on first- and second-order differentiation cannot be applied when the si gnal function is corrupted by noise. The proposed technique can be used for lead inspection of surface mount devices in the electronic industry. (C) 2 000 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)0170 5-0].