| 摘要 |
A method and system for calibrating optical reader systems employs a target with areas comprising linear gray scale levels. The gray scale levels include the darkest and the lightest scenes. The gray scale levels are illuminated by an array of LEDs and the light reflected from target impacts photo-transistors. The photo-transistors are biased in their linear ranges and the target is scanned while the LED drive current is changed. The photo-transistor responses to the different gray scale levels at the different LED drive currents are analyzed, and the LED rive current that produces a linear output from the photo-transistors over the gray scale dynamic range is selected. Several video channels may be used and their offsets and gains are normalized. Black offsets and black to white gain correction functions are generated for balancing or correcting each pixel. The correction functions may be applied by a processor for later raw image data of scenes scanned by the optical reader. |
