A fine-tuning mechanism comprises a rotating insert (100), a wheel body (200), and a cover plate (300). The rotating insert (100) has a first positioning portion (102), is rotatably mounted to the wheel body (200), and is movable with respect to the wheel body (200) along a rotation center line thereof. The cover plate (300) is fixed with respect to the wheel body (200), and comprises at least two second positioning portions (301). The at least two second positioning portions (301) are arranged surrounding the rotation center line of the rotating insert (100). When the wheel body (200) moves to a first position, the first positioning portion (102) forms a projection-receptacle engagement with one of the second positioning portions (301). When the wheel body (200) moves to a second position, the first positioning portion (102) is disengaged from said second positioning portion (301). When fine-tuning is desired, the rotating insert (100) is moved to the second position to disengage the first positioning portion (102) from a second positioning portion (301), such that the rotating insert (100) can be rotated by a certain angle, and then the rotating insert can be moved to the first position to engage the first positioning portion (102) with the next second positioning portion (301), thus realizing fine-tuning.L'invention concerne un mécanisme de réglage fin qui comprend un insert rotatif (100), un corps de roue (200) et une plaque couvercle (300). L'insert rotatif (100) comprend une première partie de positionnement (102), est monté avec faculté de rotation sur le corps de roue (200), et est mobile par rapport au corps de roue (200) le long d'une ligne centrale de rotation de celui-ci. La plaque couvercle (300) est fixe par rapport au corps de roue (200), et comprend au moins deux secondes parties de positionnement (301). Les au moins deux secondes parties de positionnement (301) sont agencées autour de la ligne centrale de rotation de l'insert rotatif (100). Lorsque
