Method for using digital projectors in collimating image disp ay apparatus

A method of treatment of a rear projection screen 1 in the construction of a collimating image display apparatus suitable for flight simulation employing digital projectors, in which the positions of the projectors are not constrained by the presence of reflected light from the inner surface of the rear projection screen. The treatment involves applying a surface covering in at least some areas with a paint or any amorphous liquid which once applied dries to a suitable coat scattering light in all directions. The coating may be applied as a layer of soft gel with a removable backing sheet, or the internal, or concave face may be treated using liquid abrasive paste or mechanical action.