Optical Bar Code Image Positioning Theory And Application

Based on barcode recognition and machine vision technology, optical barcode image positioning (OBIP) has been widely applied in photoelectric automatic measurement fields. Though the barcode recognition technology has been well developed nowadays, the case is not the same with study about the OBIP, especially about the wide range OBIP with sight stadia greatly varying. The involved international research fruits are applied to products which have been monopolized by a few foreign companies. Due to the patent reasons, the published research documents can hardly be found. However little domestic effort has been made on OBIP, which is responsible for the domestic production blank record of those products. With this background, in this thesis we will study systematically the mechanism of-OBIP and develop the positioning algorithm of high-density barcode at long sight stadia.First we meet the long-term need for domestic study about the coding and decoding principle of displacement barcode which is the basis of OBIP, and conclude the barcode ruler designing rules and general positioning algorithm.Two problems need to be solved for positioning with varying sight stadia. One is the high-density barcode detection at long sight stadia, the other is the switching between different detecting methods used for different density barcode signals when the sight stadia vary. For the first problem, we'll find suitable methods in spatial domain for different density barcode signals; and for the second one, we propose a magnification calculation algorithm in frequency domain based on the particular structure of uniform distance between bar centers. This algorithm works at different sight stadia, which makes the detection methods switching easily performed.Sinusoidal barcode is worth to be studied for its unique characteristics in coding and decoding principle, but few concerned documents have been found. In this thesis, we propose a positioning algorithm based on detecting method in frequency domain and phase calculation without the need to detect the bar widths with pretty high precision. The experimental results prove the precision of this algorithm. Then we further introduce a new barcode structure along with its positioning algorithm. With it, the utilization ratio and error tolerance will be greatly improved.Finally the research fruits in this thesis are applied to digital leveling. With a prototype of digital level produced and the corresponding program developed, a great deal of experiments are made and the test precision is close to State first-order standard of digital level.