| 摘要 |
PURPOSE:To reduce the fluctuation in magnifying power due to temperature change by a method wherein the fluctuation of projection magnifying power due to the temperature change of a projection lens is nearly offset by the distance fluctuation due to temperature change in a reticle and a projection lens. CONSTITUTION:Multiple posts 4 are fixed between a base 5 and a column 2 to provide the distance (d) between an incident iris diaphragm (ep) of a projection lens 3 and the pattern surface of a reticle R with specific design value. Said posts 4 with pertinent thermal expansion coefficient subject to the expansion and contraction corresponding to temperature changes make the distance (d) fluctuate slightly. In such a constitution, an error in magnifying power DELTAM due to any temperature change can be self-corrected (offset) by means of specifying the material and dimension of posts 4 so that the reticle R may be displaced upward by DELTAd when the temperature change is +DELTAt from the reference specified temperature. |
