There is provided an optical engine for a navigation device including a first light source, a second light source, a lens, a carrier member and an image sensor. The carrier member has a light holder, a lens holder, an accommodation space and a tilted wall. The first light source is arranged on the light holder of the carrier member, and reflected light associated with the first light source penetrates through the lens to propagate to the image sensor inside the accommodation space. Reflected light associated with the second light source penetrates through the tilted wall of the carrier member to propagate to the image sensor.