为什么我的手机屏幕在检测到目标时会变白？

I'm new to augmented reality, and I'm using vuforia 4.2.3 and unity 5, I followed all the steps trying to make a test run and whenever the camera detects the target the whole screen turn white, I've tried many thing but none of them worked, can someone help me?I'm new to augmented reality, and I'm using vuf