Dark screen on Dell laptop

Hi, The screen on my Dell laptop (which is 14 months old, not dropped or otherwise damaged) keeps blanking out although I can still see the Desktop and whatever else is on the screen if I shine a light directly onto it. This seems to happen randomly and either stays dark (until restart) or comes back on after a minute or two. The laptop doesn't seem to be overheating or making any odder than usual noises. Any ideas or help much appreciated.