The active area of the device is surrounded by an aperture on the inside DMD window surface that masks structures of the DMD chip assembly from normal view, and is sized to anticipate several optical operating conditions. Overfill light illuminating the window aperture can create artifacts from the edge of the window aperture opening and other surface anomalies that may be visible on the screen. Be sure to design an illumination optical system that limits light flux incident anywhere on the window aperture from exceeding approximately 10% of the average flux level in the active area. Depending on the particular optical architecture, overfill light may require further reduction below the suggested 10% level in order to be acceptable.