| 摘要 |
PURPOSE:To quantize a read signal accurately and to extract only a necessary pattern signal securely by adding a bias signal to a specific part of a read signal obtained from a body to be read which has an area differing in a reflection coefficient. CONSTITUTION:A window detecting circuit 8 detects the window part 2 of window postal matter P from the read signal (e) and outputs a window signal to a window decision circuit 9. Then, the window decision circuit 9 counts the frequency of the generation of the window signal and when the window signal is generated at a specified frequency, a window part 2 is decided to supply a decision signal to an adding circuit 10. Then, the adding circuit 10 adds the bias signal to the specified part of the read signal (e) other than the window part 2. The background value of the postal matter P is detected by an addition signal (f) outputted from the adding circuit 10 and its detection signal (g) and the addition signal (f) are compared with each other by a comparator 13 to perform quantization. Consequently, the read signal is quantized accurately to extract only the necessary pattern signal securely. |
