I have tried one workaround to resolve this problem.
Click scan button using appium(I assume) - for example you can write a script to click on this button every 10 seconds.
Challenge : Challenge is to point the camera to the next barcode as soon as first scan is complete.
Possible solutions - I believe that all the bar codes can be captured in a file in a pc. Copy these bar code images in a ppt or using any other program so that these images can automatically displayed one by one. Put your device in front of this pc as you are already planning to use tripod stand etc. Focus them on screen(may be first time you might need to do all these adjustments). Run your script. Do some trial runs. Synchronize the process with correct time outs. I think this should be feasible way to automate this scenario.