| 摘要 |
Light from a bulb is projected through the microfiche transparency by a condensor and a projection lens system and the projected image therefrom is passed through a prism to viewing screen means. The prism has a flat or curved, transparent entrant surface for receiving the projected image, a flat, transparent exit surface facing the viewing screen means, a first, metal coated reflecting surface opposite to the entrant surface and forming a predetermined acute angle with the exit surface such that a major portion of the light beam passing through the entrant surface is reflected by the first reflecting surface to the exit surface at an incident angle greater than the critical angle for total internal reflection by the exit surface and a second, metal coated reflecting surface angularly facing the exit surface for returning the light beam reflected internally by the exit surface back to the exit surface at an incident angle which is less than the critical angle such that the returned light beam passes through the exit surface to impinge on the viewing screen means.
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