Two dimensional code reading apparatus

A two-dimensional code reading apparatus comprising:

• a CCD sensor that captures an image including a two-dimensional code by optically scanning the image along scanning lines, the two-dimensional code being a rectangular matrix of cells, the two-dimensional code including a data field and three orientation symbols, the orientation symbols having the same pattern, located at three corners of the matrix, respectively, the data field and the orientation symbols each consisting of a given number of the cells, respectively, the CCD sensor outputting scanning line signals having signal levels corresponding to the brightness of portions of the captured image on the scanning lines;
• a single binary-coding circuit that codes the scanning line signals outputted from the CCD sensor into binary-coded scanning line signals according to the signal levels of the scanning line signals, and outputs the binary-coded scanning line signals;
• a frequency component ratio detecting circuit that compares a frequency component ratio indicated by portions of the binary-coded scanning line signals outputted from the binary-coding circuit with a single reference frequency component ratio corresponding to the pattern of the orientation symbols so as to detect portions of the binary-coded scanning line signals showing the reference frequency component ratio and to provide orientation symbol signals indicative thereof;
• memory means for storing the binary-coded scanning line signals as image data at memory locations indicated by addresses each corresponding to coordinates on the image captured by said CCD sensor;
• an address latching circuit that determines coordinates on the captured image to which the orientation symbol signals provided by the frequency component ratio detecting circuit correspond according to a timing of signals output by the frequency component ratio detecting circuit, and writes the determined coordinates in the image data stored in the memory means;
• and
• a CPU that reads the image data, in which the coordinates of the orientation symbol signals are written by the address latching circuit, from the memory means to determine positions of the orientation symbols in the captured image based on the coordinates of the orientation symbol signals, and reads data represented by the two-dimensional code based on the positions of the orientation symbols.