An optical path adjusting device comprising: a rotating unit that comprises and is arranged to rotate about a through-hole through which light passes; at least one moving unit that is movably disposed relative to the rotating unit and is linearly movable between an advance position corresponding to the through-hole and a retreat position outside the through-hole; a transmitting unit that is disposed between the rotating unit and the moving unit and transmits a rotational force of the rotating unit to the moving unit; and an optical unit that is disposed on the moving unit for blocking at least part of light passing through the through-hole; wherein: the moving unit comprises a first slider and a second slider that are movable toward each other or away from each other; and the first slider and the second slider open the through-hole at the retreat position by moving away from the through-hole; characterised in that: the first slider and the second slider close the through-hole at the advance position by contacting each other; the optical unit comprises a first liquid crystal device and a second liquid crystal device that are respectively disposed on the first slider and the second slider and operate by receiving an external signal to pass or block light; and the first liquid crystal device and the second liquid crystal device pass light therethrough at different times. a rotating unit that comprises and is arranged to rotate about a through-hole through which light passes; at least one moving unit that is movably disposed relative to the rotating unit and is linearly movable between an advance position corresponding to the through-hole and a retreat position outside the through-hole; a transmitting unit that is disposed between the rotating unit and the moving unit and transmits a rotational force of the rotating unit to the moving unit; and an optical unit that is disposed on the moving unit for blocking at least part of light passing through the through-hole; wherein: the moving unit comprises a first slider and a second slider that are movable toward each other or away from each other; and the first slider and the second slider open the through-hole at the retreat position by moving away from the through-hole; the moving unit comprises a first slider and a second slider that are movable toward each other or away from each other; and the first slider and the second slider open the through-hole at the retreat position by moving away from the through-hole; characterised in that: the first slider and the second slider close the through-hole at the advance position by contacting each other; the optical unit comprises a first liquid crystal device and a second liquid crystal device that are respectively disposed on the first slider and the second slider and operate by receiving an external signal to pass or block light; and the first liquid crystal device and the second liquid crystal device pass light therethrough at different times. the first slider and the second slider close the through-hole at the advance position by contacting each other; the optical unit comprises a first liquid crystal device and a second liquid crystal device that are respectively disposed on the first slider and the second slider and operate by receiving an external signal to pass or block light; and the first liquid crystal device and the second liquid crystal device pass light therethrough at different times.