| 摘要 |
<p>PURPOSE: To avoid the temperature fluctuation in measured values for giving high measuring precision by controlling a local airconditioner so that the air temperature on an optical path may be almost equal to the atmospheric temperature near the optical path. CONSTITUTION: Due to the existence of a heat generating source such as a stage 8 etc., in a chamber 16, the temperature distribution is made so that the air inside the chamber 16 may be a little bit higher than the air temperature fed from an air supply port 1. At this time, a control device 21 controls an air blower 6a so that the stmospheric temperature on an optical path 10 may be almost equalized with the air temperature blown in the optical path 10, i.e. the temperature data a and c may be almost equalized with each other. Furthermore, the air blower 6a is controlled so that atmospheric temperature on another optical path 11 may be almost equalized with the air temperature blown in the optical path 11 i.e., the temperature data b and d may be almost equalized. Resultantly, the fluctuation in the positional measured values due to the mixture of two fluids having temperature difference (measurement error) can be avoided thereby enabling the stage 8 etc., position to be measured with high precision.</p> |
