A nonlinear PDE based edge detection for image measurement

Image measurement technique is a new developing method in the non-contact measurement and instrument field, where image edge detection is an important factor for the measurement precision, especially in the case of blurry edges and additional noise in the image. We present an adaptive nonlinear PDE process, which has two steps: first, we use a bidirectional flow (BDF) equation to sharpen and smooth edges of the image, where an inverse diffusion is performed to sharpen edges along the normal directions to the isophote lines, while a normal diffusion is done to remove noise and artifacts along the tangent directions; second, we use the classic differential operator to detect edges. Experimental results on real images demonstrate that, based on sharp and smooth edges, our algorithm can locate edges accurately and thus may promisingly produce more exact measurement.