An imaging system comprising: a first lighting device that emits terahertz waves at a first quantity of light emission in a first operation mode, and emits terahertz waves at a second quantity of light emission, which is larger than the first quantity of light emission, in a second operation mode; a first detection device that detects reflected terahertz waves by a target and a control device that switches from the first operation mode to the second operation mode in a case where the first detection device detects the target in the first operation mode.