Wileless pen input device

PURPOSE: A wireless pen input device is provided to uniformly keep a change of motion based on a change of a location and a direction. CONSTITUTION: A lens module(150) converts light applied from a light source into parallel light. The lens module generates a different light route for a stepped difference of a bottom. An image sensor(130) senses a different light route according to the stepped difference of the bottom. The image sensor converts the sensed signal into an electric signal. A controller calculates a location change according to change during spatial location and direction movement of a pen module using the converted electric signal.