Abstract: A dual mode projection display apparatus for portable electronic device comprises: a projection device, a built-in screen, an input device and a wired or wireless connector to said portable electronic device. It has dual operation mode: in the first mode, it produces an image onto the built-in screen; in the second mode, it produces an image onto any external surface with substantially high reflectance/scattering. When connected with a smartphone, the apparatus provides a big screen and convenience input method for the user. The invention increases the functionality and utility of a smartphone.