A two-dimensional bar code reader
Nicolas Normand, C. Viard-Gaudin · 2002
As an alternative to the use of laser scanners for bar code readers, we have developed a global solution based on a 2D vision system. It is composed of two main functions: bar code localization on the overall image, and the reading stage. The localization of the symbol which can be oriented in any direction is carried out with an original method which relies upon the extraction of high density area of mono-oriented gradients. The reading method is based on the detection of the transitions between the stripes by extracting the zero-crossings of the second derivative of the 1D signal reconstructed from the 20 bar code block. This system has been tested on several hundred images, the results show a global success rate (localization and decoding) of 100% within a wide range of acquisition parameters, resolution and depth of field, as the camera is not auto-focused the images can be deeply blurred.