To secure object visibility at all times by surely identifying, specifying and optionally controlling only the light incident directly on eyes of sports players or workers, in floodlights in a sports arena or a construction site at night.

Lumious intensity of the floodlight system 10 is modulated by such a high frequency which is hard to be visually recognized by humans, or at such weakn intensity that humans are not aware of it. The means enabling the recognition is change of the modification frequency. A modification phase is changed even at the same frequency. Or the identification sign of each light source is realized by including a two-valued signal in a modification content. A light sensor on the targeted person side is set on the head near his eyes, and the aspect of the received light is processed as it is or after identification, and it is sent to a control device 17 through radio, so that the control device 17 individually controls and dims the light source specified.