Abstract: A system where boxes (12) move along a conveyor belt and a bar code scanner reads bar codes (20) on the boxes and detects the presence of a box (with or without a readable barcode), which facilitates establishing a box detector that detects the leading edge of a box. The bar code scanner has a scanning laser beam source (30) that directs a scanning laser beam (32) at the path of bar codes on the boxes, and a sensor (44) that detects reflections of the laser beam, so the output from the sensor can be used by a bar code reader (52) to read bar codes. Instead of setting up a separate box detector, the output from the laser reflection sensor is delivered to a container detecting circuit (102) that uses the output of the laser reflection sensor to detect the leading edge of the box.

Abstract: A bar code scanner/verifier rapidly analyzes reflections of a scanning laser beam to determine whether or not a scanned line portion contains a bar code, so analysis of a bar code begins only when a legitimate bar code is present. The apparatus reads transitions in reflectance and indicates that a bar code is not present when the transitions are not large enough to qualify for a bar code, and when there are not enough transitions per unit distance. The circuit does this by generating MAX minus MIN, where MAX continually decreases over time but is raised every time a high reflectance is encountered, and MIN continually increases over time but is lowered every time a low reflectance is encountered. When MAX minus MIN drops below a programmable predetermined noise level, the circuit indicates that there is no bar code.