A digital mirror dence chip has a substrate, micro-mirrors disposed on the substrate, and a glass cover plate disposed over the micro-mirrors. Each micro-mirror is inclined by +10 degrees or −10 degrees with respect to the substrate to be set to an on-state or an off-state. Incident light produced in a lighting source system is totally reflected in a total internal reflection prism and is incident on the micro-mirrors through the glass cover plate. Outgoing light reflected by micro-minors in the on-state passes through a projection lens and is projected onto a screen to form an image on the screen. Also, outgoing light reflected by micro-mirrors in the off-state passes out of the projection lens. The glass cover plate is not parallel to the substrate. Therefore, light specularly reflected by a surface of the glass cover plate passes out of the projection lens.