| 摘要 |
PURPOSE: To observe a projected picture formed on a screen at an easy-to-see angle by setting the prism angle of a variable angle prism provided in an optical path to be varied. CONSTITUTION: A screen 10 is arranged nearly perpendicularly to a set surface. The variable angle prism (variable apex angle prism) 11 is provided near the back (observation side) of the screen 10. The prism 11 has transparent silicone rubber being high-viscocity fluid substance inside, its transmitting surface is constituted of thin glass plates (transparent parallel plates) 11a and 11b, and its outer periphery part is surrounded by metal, then it acts as a transparent plane parallel plate in an ordinary state. The prism angle (apex angle)θof the prism 11 is set to be varied by pressing the peripheral part of the glass plate by a prism angle varying means. By optionally changing the prism angleθ, the observing direction of the screen 10 is optionally changed.
|
