We have developed an inspection system that reads a ring bar code stamped on data recording discs, such as CDs and DVDs, with a high degree of accuracy and at high speed by using image processing technology. The system uses the following two methods to achieve high reading speed : a method of bar code position detection which uses a reduced number of reference pixels, and a method of brightness addition data production which determines the bar code thickness based on a polar projection table. The system allows us to inspect ring bar codes with a minimum element width of 130 μ m and 22 characters in approximately 250 ms (less than 1/3 the time required by the conventional method).
