Screen goes dark after 5 seconds while sitting at the Lock Screen

Hi. I have an iPhone 4 that I connect to a third-party stereo via an special accessory cable that plugs into the iPhone docking plug. When music is playing on the iPhone, the screen eventually falls asleep and goes dark.

When I wake it up by pressing the Home button it turns the screen back on and the phone is at the Lock Screen. The background of the Lock Screen is the album art of the song that is currently playing - which I like to see very much!!!

The problem is that the screen immediately goes dark again within about 5 seconds so the album art is not continuously displayed. My question is - is there a way to keep the iPhone from going dark when it's at the Lock Screen? After waking it up it only stays on for about 5 seconds and then goes dark again.

Any thoughts would be greatly appreciated.