This paper proposes a new vision-based active sensing system, termed vision-based active antenna. This is composed of a camera, a flexible beam whose force-deformation characteristic is known, and an actuator for rotating the beam. The camera observes the beam deformation, including the contact information, while the beam is in contact with an object. By solving a set of equations based on the information acquired through the camera, the sensor can detect the contact location, the contact force, and the stiffness of the object, even though the contact point is hidden by occlusion. For two particular versions, we show some experimental results to verify the basic idea.