An apparatus (200) for increasing field of view of optical system is provided. The optical system includes a lens module (20). The apparatus comprises a rotational mechanism (30) rotatably mounted in the optical system. The rotational mechanism includes a refraction means disposed on an optical axis of the lens module and configured for refracting a light signal from outside of the optical system into the lens module. The apparatus may be used in optical systems, such as camera modules, digital video cameras, image pick-up systems used in cars, infrared optical systems, projection optical systems, and real-time detector systems.