| 摘要 |
1280977 Optical projections CHARLES FRANK Ltd 19 April 1971 [15 April 1970] 17850/70 Heading G2A The projector 10 includes two lamps 13, 16, fan 16A, pivotable mirror 20, Fresnel lens 12, objective lens 17, a support 14 carrying an overhead lens system (not shown) and a screen (not shown) on to which images passing through the lens 17 or overhead lens are projected. As shown plate 8 masks the lens 12. This plate carries an opaque object on to which light from lamp 16 falls and is reflected by the mirror 20 through lens 17 to the screen. When the plate 8 is removed and mirror 20 retracted to the position shown by the dotted line lamp 13 illuminates information on transparent sheet 9 which can transfer between two rollers (not shown) on either side of the lens 12 and the image projected by the overhead lens to the screen. Arm 21 has notches 21A and associated micro-switches (not shown) corresponding to the two described positions of the mirror 20 in which the required lamp only is illuminated. A third intermediate notch is provided in which the lamps 13, 16 are both illuminated at low power to prevent current surging in the cold bulb filaments. In a modification the plate 8 may be apertured and the Fresnel lens 12 made removable so that bulky opaque objects can be supported by the apertured plate and episcopically projected through lens 17 as already described.
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