A method of projecting a compensated principal image may include projecting a principal image onto a surface and projecting an intended calibration image onto a calibration area of the surface. A material gas of Si is then supplied at a flow rate of 1 mLmin. A latch may be used to latch the pivotal jaw to the fixed jaw. This rendering processing is executed for all polygons, and the final image data Dn is used as image data for display.