| 摘要 |
PURPOSE:To stabilize imaging characteristics such as projecting magnification and the position of an imaging plane, etc. by passing air into the inter-lens spacing of a part of a projecting lens, monitoring further the change in atm. pressure and outdoor air temp. and controlling the pressure in the other inter- lens spacing of the projecting lens. CONSTITUTION:A microcomputer (CPU)22 reads out via an interface 25 the respective outputs from a pressure detector 20, a temp. detector 21 and an environment sensor 23. The CPU operates a pressure control part 18 according to the measured values of the atm. pressure, the temp. of the outdoor air, the temp. of a lens L5 and the pressure in a spacing 2 obtd. in the above-mentioned way thereby controlling the pressure of the spacing 24. The magnification error of a projecting lens 1 is thus made zero. The CPU22 operates a stage driving part 26 to adjust the position of the imaging plane. The CPU controls further a fan 4 to feed air to the spaces 10, 11, 12 thereby making zero the magnification error owing to a temp. rise. The imaging characteristics such as imaging magnification and position of the imaging plane, etc. are thus stabilized. |
