Compact Coaxial Thermal and Color Imaging System with Silicon-Glass Hybrid Lens

Detecting human is one of the most important functions of service robots assisting human lives. Thermal images are useful to detect human. Since the number of pixels of the thermal imagers is smaller than that of color imagers, thermal images get more useful combined with corresponding color images. In this paper, we propose a compact optical system to obtain both thermal and color images simultaneously. The key is to use a silicon-glass hybrid lens, with which visible and far-infrared light can be focused. The focused light was split by a silicon plate. The thermal and color images were taken by a thermal and color imager, respectively. We experimentally showed that the focal plane was tuned by the position of the lens keeping the correspondence of thermal and color images.