*4.2. Registration on Real Face Images of Self-Built Multi-Spectral Database*

In order to demonstrate the performance of our registration in the high-resolution multi-spectral imaging system, we built a four degree of freedom (DOF) pan and tilt head vision platform for multispectral database acquisition, which can be seen in Figure 6.

**Figure 6.** 4-DOF pan and tilt head vision platform for multi-spectral database acquisition: (**a**) Design mechanical model of vision platform; (**b**) Image acquisition scenario.

This 4-DOF pan and tilt head vision platform can realize up-down pitch movement and left-right yaw movement, respectively. Moreover, a Belgium Raven-640-Analog thermal infrared camera with 10 mm short lens is used to acquire a 74◦ × 59◦ field of view (FOV) infrared image (Figure 6a left), while a DAHENG MER-310-12UC color camera with an Optotune EL-10-30-Ci variable-focus liquid lens is used to acquire a 28◦ × 22◦ FOV visible image (Figure 6a right). Meanwhile, a visible image is always taken simultaneously with the infrared image to form a multi-spectral image pair, and the visible and infrared images are both compressed into 640 × 480 pixels. The multi-spectral vision equipment and image acquisition scenario is shown in Figure 6b. The self-built multi-spectral database is composed of 20 different individuals involving different illumination conditions and pose variations. In addition, for each individual, the sampled images are captured from 13 different angles (tilt head from −90◦ to +90◦) and two illumination conditions (dark and light).
