| 摘要 |
PURPOSE:To prevent the reading of a bar code with low printing density and noise by generating a first detection signal when a designated period of time has passed since the latest bar code was detection and generating second and third detection signals when a first bar code is detected. CONSTITUTION:By utilizing a bar code detection signal S3 outputted from a bar code detection signal generator 20, a level compensation circuit 18 is operated and a black level detector 13 is controlled so as to lower black level voltage EAB by a certain amount. The bar code detection signal generator 20 generates bar code detection signals S2 and S3 and stops generating a bar code detection signal S1 at the same time. Accordingly, a lower limiter 17 stops operation, and with the operation stoppage, the black level detector 13 is controlled by the level correction circuit 18 and the level of the black level voltage EAB is lowered. Thus, the black level and white level of an output signal E1 of a current/voltage converter 12 are immediately followed and the reading of the bar code is executed with high accuracy. |
