Robust car License Plate Recognition system verified with 163, 574 images captured in fields

We have been manufacturing our own License Plate Recognition (LPR) systems since 1999 for parking lots in Japan. We have implemented a number of enhancements for our latest LPR system and one of the most important enhancements is for ranges of acceptable license-plate attitude angles. We collected 163, 574 actual images so far and we selected 6,648 images randomly from this image database to verify our latest design. The histograms of plate attitude angles are estimated for these 2,836 images by measuring the license-plate shapes in the images and analyzed statistically. The analysis results for these actual 2,836 images prove that our latest LPR system accepts the attitude angles within its product specifications with enough margins.