After updating my Lumia 525 sometimes its screen is blinking, what could be wrong?

when i bought the product Lumia 525 with window 8 it was fine but now i have updated it to window 8.1 , now some times during process it starts blinking. I restarted it and tried a lot but there is no change in pattern still same. Suggest me what to do .

What do you mean with blinking. That the display becomes more bright or less bright. If this is the case it is due to AUTO BRIGHTNESS SETTING.

ITS DONT LIKE more or less brightness..its like few lining across the screen for few seconds..and after that its normal