| 摘要 |
PURPOSE:To enhance durability and to scan an image with high accuracy at high speed by forming the wall surface of the fitting hole of a laser beam scanning polygonal mirror made of glass of a finished surface where fine unevenness is removed and forming a strengthened layer which is chemically strengthened on the finished surface. CONSTITUTION:The wall surface 39 of the fitting hole consisting of an inner peripheral surface 39A and chamfered parts 39B on both sides is obtained by grinding the central hole 45 of an annular plate-like base material 43 and then polishing it with high accuracy to a completive dimension. By performing polishing, the finished surface where unevenness is removed and the turning of glass is taken away is obtained. Then, the strengthened layer 41 is formed on all the surface of the base material 43 including the wall surface 39 of the fitting hole 35 by emmersing the material 43 in a chemical strengthening tank and performing chemical strengthening for a necessary time. In order to form the strengthened layer 41, the base material 43 is emmersed in the heated tank with potassium nitrate for several hours to substitute Na in a glass surface layer of K and structure in the glass surface layer is made denseness. |
