Real-time license plate detection system with 2-level 2D Haar Wavelet transform and Wiener-deconvolution vertical edge enhancement

Against lots of conventional vertical-edge-based License Plate Detection (LPD) systems, this paper presents a robust and real-time LPD system to differentiate the strength and density of vertical edges between the license plate region and non-plate regions. The proposed LPD system consisting of 2-level 2D Haar Wavelet transform and Wiener-deconvolution vertical edge enhancement not only can highlight the irregularly-distributed vertical edges of the license plate region, but also can suppress the regularly-interlaced ones of the non-plate regions, like radiator grilles or trench grates. Experimental results show the proposed LPD system achieves better detection rate than numerous conventional vertical-edge-based LPD systems, under various complex conditions. Thereby, the License Plate Recognition system based on the proposed LPD system is also verified to accomplish superior recognition rate at the cost of only 0.3 sec per frame on the dual-core smartphone platform.