An apparatus for adjusting a distance between first and second elements, comprising a first rotation member (200) rotatable between first and second stop positions and a second rotation member (300), wherein rotation of the first member between the first and second stop positions comprises a first rotation stage in which the first rotation member rotates through a first rotation angle and a second rotation stage in which the first rotation member is configured to engage with the second rotation member to rotate the second rotation member through a second rotation angle.
