An exemplary mechanical shutter includes a barrel, a first blade, a second blade, a third blade, a magnet, and a magnetic field generator. The barrel defines a through hole and an aperture in the hole. The first blade is arranged in the hole and mounted on the barrel. The second blade is slidably mounted on the first blade. The third blade is slidably mounted on the second blade. The magnet is attached to the third blade. The magnetic field generator is mounted on the fixture and spatially corresponding to the magnet. The magnetic field generator applies a magnetic field to the magnet. The magnet and the magnetic field generator cooperatively move the blade group between an extended position and an retracted position.