7.6.4 Illumination Overfill

The active area of the device is surrounded by an aperture on the inside DMD window surface that masks structures of the DMD device assembly from normal view. The aperture 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 included in the projected image. To reduce DMD heating when applying high incident flux levels to the DMD in high power applications, design the illumination optics to limit light flux incident anywhere outside the active array to nearly zero percent. For lower incident power levels, depending on the optical architecture of a particular system, the acceptability levels of overfill light must be determined by the user as it relates to a specific application. In most cases it is almost always held to zero.