Android: How to turn off device screen's backlight without stopping the app

Question

Is there a way to programmatically turn off the device screen's backlight (even if it will require a root access), without stopping the application. I've tried to set the minimum brightness level, but it keeps screen on. I need something that will completely turn off the screen, without sending the device to sleep.

Short about the app: The app is a launcher app, and it will be embedded in the ROM, so the app will have root access.