infrared radiations from the Sun that are invisible to the human eye人眼不可见的太阳红外辐射

searching with infra-red scanners for weapons and artillery用红外扫描仪搜寻武器和火炮

At night infrared cameras track these birds even as they sleep.在夜晚, 红外摄像机记录这些鸟的行踪, 包括它们睡觉时的情形。