| 摘要 |
PURPOSE:To prevent a projected image from fluctuating, by providing a means of holding constant the temperature of air between an optical image-formation system and a body to be observed. CONSTITUTION:In a projection grinding machine, for example, a slidable air shielding hood 26 is fitted to the relay lens barrel 7a of an optical image-formation system and then fixed with a metal fitting 22. A hood body 23 is provided with an opening 24 for the replacement of a grindstone 27 and grinding operation. Conseqnently, the temperature of air between the optical image-formation system and a body to be observed is held constant, so that a projected image is prevented from fluctuating. |
