correction buttons for correcting the shape of images to be projected for display every time the user operates any of such correction buttons the cpu 400 makes the distortion correction section 430 execute the procedure of fig5 in step s 102 the target display area determination section 432 acquires the shift and zoom positions of the projection system 340 more in detail the target display area determination section 432 makes the shift position detection section 362 detect the shift position of the projection system 340 so that the resulting detection values current values are acquired the target display area determination section 432 also makes the zoom position detection section 364 detect the zoom position of the projection system 340 so that the resulting detection values current values are acquired in this embodiment the projection system adjustment section 350 is capable of adjusting the shift and zoom positions of the projection system 340 in response to user issued commands with this being the case instead of the detection values as the current values of the shift and zoom positions the control values of the shift and zoom positions provided to the projection system adjustment section 350 may be acquired in step s 104 based on the detection values current values of the shift and zoom positions of the projection system derived in step s 102.