A degassing from a susceptor heated at a high temperature in a vacuum atmosphere is suppressed. The first substrate is curved along a first direction and includes a pixel area through which light is transmitted and a non-pixel area which blocks light transmission therethrough. First and second devices, such as surgical lights, a cameras, and monitors, are mounted to a first end of a first device arm and a first end of a second device arm, respectively. The pilot symbols conform to a rank-deficient pilot mapping matrix.