| 摘要 |
PURPOSE: To prevent the mispositioning of a rotary polyhedral mirror by a temp. change. CONSTITUTION: A stationary shaft 22 made of ceramics is erected in a housing 21. A revolving sleeve 23 made of ceramics is fitted to this stationary shaft 22. A receiving member 24 made of aluminum having a coefft. of thermal expansion of about 22×10<-6> K<-1> or made of brass having a coefft. of thermal expansion of about 20×10<-6> K<-1> is fixed to this revolving sleeve 23. The upper surface of this receiving member 24 is provided with a fitting projection 24a and is provided with a gap part A between the inner peripheral surface of this fitting projection 24a and the outer peripheral surface of the revolving sleeve 23. The depth of this gap part A is set equal to or larger than the height of the fitting projection 24a. The rotary polyhedral mirror 31 made of aluminum having the coefft. of thermal expansion of about 22×l0<-6> K<-1> is placed on the receiving member 24 in such a manner that the annular projection 24a fits into the fitting hole 31a. The receiving member 24 and the rotary polyhedral mirror 31 expand and contract approximately equally and the fitting projection 24a expands and contracts freely into the gap part A, thereby preventing the change in the position of the rotary polyhedral mirror 31. |
