| 摘要 |
PURPOSE:To freely select an angular aperture of a projection light beam, without being bound by the condition in the hollow member side, by forming a projection window member in the form of a rod, and bending its center shaft. CONSTITUTION:A projection window member 13 is formed in a round rod by use of a transparent material, and its center shaft is installed so as to face the projection direction side. The base end side part 15 is bent by curvature having the center Op, the tip side part 16 is bent by curvature having the center Oq on the reverse side, and the curvature radius of the base end side part 15 is formed so that it becomes longer than that of the tip side part 16. Also, the circumferential surfaces of the base end side part 15 and the tip side part 16 are formed so as to continue smoothly. The center shaft of the extreme tip part of the tip side part 16 is parallel with the direction of the center shaft in the extreme tip part of the tip side part 16. |
