Projection Apparatus (1917)

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Bausch & Lomb Optical Company uninterrupted passage of light through to the lantern slide projection lens. The attachment is provided, of course, with an individual condensing lens, which forms the third member of the triple system for vertical projection, and with a regular quality projection lens of ljHs-inch diameter, 10-inch focus. Attachment for Projection of the Spectrum and Complementary Colors Figure 8 —Set of Accessories for Projecting Spectrum and Complementary Colors with Model D Balopticon. Figure 8 illustrates the Model D Balopticon equipped for projection of the spectrum and complementary colors. The bellows are removed and the standard, carrying an adjustable slit, attached to the lantern bed between the slide carrier support and the front standard. The accessory optical bed, carrying the rest of the accessories, is attached to the front of the regular optical bed. If the Balopti- con has the large lamp house, a set of revolving carbon holders, desirable in showing emission spectra, should be fitted to the arc lamp. Absorption and emission spectra only may be projected by using simply the adjustable slit and the prism placed before the projection lens. 44