| 摘要 |
Test patterns (6) in bar code of different densities are printed at the start of document (20) preparation on the line with a alignment mark (5). The test patterns (6) are immediately read at different timing intervals (59) corresponding to the densities of the patterns. The highest density pattern (6) having test data which is recognized by the logic (61) as correctly sensed, defines the subsequent printing density to be used. First, the next line of data 3 is printed in the lowest density with a code defining the density of the subsequent printing. When a document (20) is read, the first line is read with the clock (59) intervals corresponding to the lowest density. The frequency is then changed to that defined by the code in the first line. Alternatively, the frequency is adjusted lower when an ordinary line of data is re-read and found to read incorrectly. |
