"We offer new support options and therefor the forums are now in read-only mode! Please check out our Support Center for more information." - Vuforia Engine Team

back camera problem

hi everyone I have samsung galaxy tab s 8.4 . if i use front camera to detected a marker but back camera don't detected . so I don't know what happen

and my marker size 4*9.5 cm but if marker bigger is can detected (haft of a4 paper). so how to fix it?? 

p.s. I use Unity3d 4.6.3 and vuforia 4 and change camera device mode is quality.

Thank you for anwser.