This paper addresses the problem of laser scanner failure on mirrors and windows. Mirrors and glasses are quite common objects that appear in our daily lives. However, while laser scanners play an important role nowadays in the field of robotics, there are very few literatures that address the related issues such as mirror reflection and glass transparency. We introduce a sensor fusion technique to detect the potential obstacles not seen by laser scanners. A laser-based mirror tracker is also proposed to figure out the mirror locations in the environment. The mirror tracking method is seamlessly integrated with the occupancy grid map representation and the mobile robot localization framework. The proposed approaches have been demonstrated using data from sonar sensors and a laser scanner equipped on the NTU-PAL5 robot. Mirrors and windows, as potential obstacles, are successfully detected and tracked.