Use your screen as a light. Source code.
It's free to get the installation package of Ultra White Screen, also, you can check out users' reviews on Droid Informer. The app works fine on Android 2.2 and higher. This download is completely safe. Stepanchenko Dmitriy is the developer of this application that can be found in the Tools category.
Over 5K users downloaded and set up Ultra White Screen and the latest update was on Feb 27, 2017. On Google Play, the app has been rated 4.3 by its users.