Abstract: A rear-projection display apparatus includes a housing, a screen mounted on the housing, an optical engine mounted in the housing, and a host unit mounted in the housing and coupled to the optical engine. The host unit includes an on screen display module having an image alignment unit that is operable in an image-alignment mode to enable the optical engine to project a test pattern onto the screen. The image alignment unit is operable to adjust display of the test pattern projected by the optical engine onto the screen such that the test pattern thus displayed is within a predefined range of the screen when the image alignment unit is operated in the image-alignment mode.

Abstract: A position-adjusting mechanism of an optical engine comprises a base, an adjusting board, two adjusting devices, two fastening devices, and a universal bearing. The adjusting board is set on the base and has two arc slots and two screw holes formed thereon. The adjusting devices are respectively screwed in one of the screw holes and set against the base. One end of the fastening device is inserted through one of the arc slots and is fixed on the base, and the other end of each fastening device is used to press the adjusting board towards the base. The universal bearing is located between the base and the adjusting board and serves as a pivot for rotating the adjusting board against the base.