| 摘要 |
PURPOSE:To reduce the cost and weight of the prism by injecting a melt radially to a prism mounting plate in the thickness direction from nearly the central part of the plate. CONSTITUTION:An injecting gate 2 is disposed nearly at the center of the mounting plate 1 in such a position where a molten liquid crystal polymer spreads radially and uniformly around the gate 2 and is thereby so devised as to sufficiently utilize the properties of the liquid crystal polymer. Namely, the liquid crystal polymer has a small coefft. of linear expansion in a fluid direction and, therefore, the difference between the coeffts. of linear thermal expansion of a prism mounting base and the prism is in a permissible range. The sufficient coefft. of linear thermal expansion is, therefore, provided over the entire part of the mounting base by injecting the polymer to the mounting base nearly from the central part. The optical performance is maintained in this way while the prism is relatively inexpensive and light in weight. |
