An input system includes a first gesture detection unit and a second gesture detection unit. The first gesture detection unit includes a first light emitting device for emitting a first light beam, a first light sensing device for receiving the first light beam reflected by a first motion trajectory generated by a user and outputting a first image signal, and a first processing unit for processing the first image signal and outputting a first command signal. The second gesture detection unit includes a second light emitting device for emitting a second light beam, a second light sensing device for receiving the second light beam reflected by a second motion trajectory generated by the user and outputting a second image signal, and a second processing unit for processing the second image signal and outputting a second command signal.