| 摘要 |
<p>Over head projector for projection of opaque matters comprising an image-forming unit consisting of a downward facing, relatively large, ring-shaped, concave mirror (5) and a smaller, upward facing, convex mirror (6) which embraces the image formed by the concave mirror (5) of the matters to be projected. The curvature of the convex mirror (6) is such that the light rays reflected from it pass through the hole in the concave mirror (5), reflect for the plane mirror (9) and form an image at a suitable distance from the projector. A glass pane (11) seals the opening on the upper side of the concave mirror (5) and another glass pane (12) closes the entire opening under the concave mirror (5) and supports the convex mirror (6). The glass panes (11, 12) stop dust from entering the reflecting surfaces of the curved mirrors. The space under the convex mirror (6) provides room for an illumination device (3) and a reflector (4). </p> |
