We own a bunch of Brother DS600 mobile scanners. The scan quality on one of them started to deteriorate. We figured out that the problem was the PC, not the scanner, as we took that scanner to another PC and the same scanner started scanning just fine, with good quality. We then tried to re-run the calibration step that is available in the device properties using the special calibration paper that comes with the scanner. We got an error message saying the calibration had failed.
We tried a bunch of things, and couldn't get the calibration to work on the 1 computer. We kept getting the error message "failed to calibrate". We searched everywhere on the internet for a solution, and couldn't find one. We even removed the driver and re-booted the computer and then re-installed the driver. That didn't work either.
Finally, we figured out that when you run the calibration initially on the computer, a file is created called "calibration.dat". This file does not get deleted when you uninstall the driver. So we searched the computer for this "calibration.dat" file and deleted it. We could then run the calibration step without any errors.
The calibration.dat file is located in the c:\programdata folder, a hidden system folder. So you have to search to find it, and then delete it. You should be able to re-calibrate the scanner then.