Reflective materials and Kinect v2 IR camera

Question

IR image of the reflective markers

Hi, I'm doing my master thesis on collaborative robotics in which I use 4 spherical markers covered with reflective tape in order to detect them with the IR camera of the Kinect. This avoids problems of noise given by the use of colored markers and RGB camera but introduces a very big limitation. I cannot retrieve depth informations of this markers!! I was wondering what is the physical explanation of this. I mean, theoretically depth informations work with TOF sensors and a reflective materials reflect back the light rays emitted, where is the problem? Thank you in advance, Ale