BAR-CODE DETECTION CIRCUIT

摘要

PURPOSE: To provide a bar code detection circuit easily manufacturable at a low cost capable of accurately reading a bar code without being affected by noise. CONSTITUTION: The slope detector of a wide band width is provided with a comparator 102 provided with first and second time constant circuits connected to first and second input. One time constant is about the triple of the other time constant. The comparator 102 responds to the slope of input analog signals 18 connected to the time constant and changes a state. Feedback is formed by a fixed resistor or a tracking circuit and a smoothing or limiting circuit is used so as to eliminate the noise from the input analog signals. A bar code read system 140 connects first and second limiting circuits 142 and 144 and smooths high and low input signals connected to the slope detector 100b. In order to form symmetrical hysteresis characteristics, the tracking circuit is used.