Patent ID: 8245936

Claim:
A method of dynamically recalibrating a bar code reader, the method comprising: reading data from multiple bar codes; while reading data from multiple bar codes, receiving a recalibration signal or an indication of an error in reading an image of a bar code imaged by the bar code reader using a lens assembly calibrated to focus using a first focal length for reading the bar code, wherein the bar code reader employs open-loop auto focus controls; in response to the recalibration signal and while reading data from multiple bar codes, measuring a distance between the bar code and a lens assembly in the bar code reader, wherein the distance is measured with a range finder carried by the bar code reader; determining a second focal length of the lens assembly that provides a better image of the bar code; and while reading data from multiple bar codes, recalibrating the open-loop auto focus controls of the bar code reader using the determined second focal length and the measured distance, and without need for a calibrated test system, wherein recalibrating the open-loop auto focus controls includes— adjusting the open-loop auto focus controls by updating a transfer function of the bar code reader stored in a memory to correct focusing errors of the bar code reader present at a time of reading the image of one of the multiple bar codes, wherein subsequent focal lengths used by the bar code reader to read subsequent images of bar codes automatically correct for the focusing errors until another dynamic recalibration of the bar code reader occurs, and wherein the recalibrated open-loop auto focus controls are used for reading a subsequent image with the bar code reader.