A fine adjustment mechanism for objective of the laser beam expander is designed.When the environmental temperature changes

adjusting the optical interval of expander to compensate the thermal deformation.The mechanism uses the screw drive

through screwing the nut to moving the objective

thus adjusting the optical interval.The mechanism have simple structure and convenient operation

the adjusting precision can reach 0.02mm.On the occasion when manual adjusting is inconvenient

the mechanism can be modified to having the having the function of automatic adjusting

the method of automatic adjusting is presented.