2 Detecting moving objects When we use a PTZ camera and background subtraction to detect moving objects, we must synchronize the PTZ of the camera and the PTZ of the background image. This paper describes a method a new method of detecting moving objects with an omnidirectional camera. The proposed method uses a fixed omnidirectional camera which can acquire images surrounding the camera, and background subtraction based on updating background image. When we subtract the background image from the input image, we consider oscillation of intensity. Therefore, the proposed method can robustly detect moving objects under the condition that there were fluorescent lights and windows which outside light came into. In the experiment, the system can detect moving objects and show the images of the objects in the room.