Bar code reading system and bar code reading apparatus with start margin detection circuitry

DETAILED DESCRIPTION An object of the present invention is to provide a bar code reading system employing high-speed scanning means for reading a bar code formed on the surface of an object that moves in a space at a high speed.
The system of the present invention can solve the problems of the conventional bar code reading technique, correctly read a bar code, and convert it into binary data, even if a slicing level is low, even if reflected light is weak, and even if irregularities on the surface of a sheet where the bar code is printed produce noise.
In order to accomplish the object, a bar code reading apparatus according to the present invention comprises a scanning portion, a collector for collecting light reflected from a bar code, a binary circuit for providing binary data according to an analog signal contained in the collected light, a bar width counter for computing the widths of bars of the bar code according to an output of the binary circuit, a demodulating portion for generating predetermined information according to values provided by the bar width counter, a bar code construction checking portion for checking the construction of predetermined parts of the bar code according to the values provided by the bar width counter, and a sequence controller for controlling the bar code construction checking portion, judging, only when the bar code has a predetermined construction, that output data provided by the demodulating portion is effective, and letting the data of the demodulating portion go out.
The bar code reading apparatus also includes an amplitude increase detecting means for detecting when the amplitude of the analog signal steeply changes.
When the amplitude increase detecting means provides a detected signal, the sequence controller acts as if there were a normal white margin in the bar code, even if at least a start margin of the bar code produce noise.