1. A method for determining an optimal exposure of a structured light based three dimensional (3D) camera system including a projecting means for illuminating a predetermined pattern on a target object, an image capturing means for capturing an image of the target object with the pattern projected, and a processing means for reconstructing 3D data based on the captured image, wherein the method automatically determines an optimal exposure level of the structured light based 3D camera system through analyzing the captured image of the target object.