Optical input device, operation method thereof and image system

The invention relates to an optical input device which comprises a first main body, a second main body and a processing unit. The first main body is used for moving on the surface. The second main body is used for moving relative to the first main body. The processing unit can calculate displacement information of the first main body on the surface and the relative change of the second main body to the first main body, control at least one cursor according to the displacement information and update pictures of an image display device according to the relative change. The invention further provides an operation method of the optical input device and an image system.