Hand Held Video Projector Nice Unit Why Are There Vertical Lines On The Screen Of My PSP Hand Held Video Game?

Why are there vertical lines on the screen of my PSP hand held video game? - hand held video projector nice unit

After loading the music on my PSP, I realized that it is very thin vertical lines on the screen. The playing well, but the vertical lines are bothering me. What are the causes and how can I rid of it?