| 摘要 |
943,346. Optical projection apparatus. J. BOLSEY. Sept. 16,1960 [Nov. 20, 1959], No. 31992/60. Heading G2J. An optical projector having a light source and condenser system, for directing light through a transparency, and an objective lens and mirror assembly, which can receive the light from said system and project an image of the transparency to a screen on which the image is viewed, is characterized in that the objective lens and mirror assembly includes a housing in which an objective lens is removably mounted, a plane mirror for reflecting light which has passed through the objective lens to the screen, and a transparent plate which is carried by the housing, which retains the removable objective lens in the housing, which is movable to render the objective lens accessible for removal and replacement, and through which the light reflected from the mirror passes. As shown (Fig. 1), an overhead projector comprises a lamp and condenser housing A, a support mast C fixed to said housing A and an objective housing B. The housing A, shown in greater detail in Fig.3,includes a lamp 30,a reflector 46 (which may be integral with the lamp 30), a movably mounted meniscus condenser lens 48, an inclined mirror 56, louvres 60 for protecting the operator's eyes from direct light, a fresnel lens 58 and a translucent plate 24 for supporting transparencies to be projected on to a screen 80. The housing A is adjustably supported on screws 104 and legs 114. The mast C is collapsible and supports the housing B (Fig. 6) which contains an adjustably inclined mirror 94, a slidable glass plate 88 and a plurality of channel members such as 84 by which one or more meniscus objective lenses in supports as shown in Fig. 8 may be removably supported. Means other than channels for supporting objective lenses are illustrated in Figs. 7a and 8a (not shown). The housing A may also contain a cooling fan and adjustable ventilating louvres (cf. Figs. 2 and 2a not shown). A modified collapsible housing A is illustrated in Figs. 11-14 (not shown) and Fig. 15 (not shown) illustrates a housing A with provision for storing the housing B therein when not in use. A pair of prisms may be used between the objective lens and plate 24 if these are misaligned. A periscope system in a housing may be attached to the projector to enable an operator facing the audience to view the projected image.
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