Projection Apparatus (1917)

Bausch & Lomb Optical Company When projecting lantern slides, opaque objects or using any of the other attachments, the body of the lantern is in the position indicated by Figure 10—lined up with the optical bed. When changing from any of these forms of projection to moving pictures, all that is necessary is to slide the Balopticon over until it lines up with the moving picture mechanism, and vice versa. Quick interchange is thus provided between moving pictures and all other forms of projection available. A stand of such construction as that shown here is necessary to give the requisite stability and to prevent vibration when running the moving picture mechanism. Specifications of Balopticon Base— Cast iron frame of rectangular shape, 11J4 in. wide, with rigid supports at either end carrying dark chamber and optical bed at height of 10 x /z in. Optical Bed Of lathe type, carefully planed, accommodating supports for attachments which may be adjusted as desired and rigidly clamped; length of optical bed proper, 25 in.; entire bed, including space occupied by dark chamber, 47 in. long, affording wide range of applicability. Lamp House —Measures 13/4 in. long, 15 in. high and 8 in. wide; light-tight and freely ventilated, constructed of double sheet metal walls, with an air space between the two walls and the roof fitted with our special, patented ventilator; provided with large, light-tight spring door on the side and obser- vation windows on both sides; mounted between uprights at front end and provided with handle at rear, permitting it to be easily tilted for opaque object projection and held rigidly in position by strong spring arm; conforms to the most rigorous requirements of Boards of Underwriters. Illuminant —Hand-feed arc lamp for direct or alternating current, connected by two feed wires to a switch attached to rear of base; provided with magnetic coils to minimize ‘blowing.” Condensing System —Our regular triple system, with the two rear lenses of 6 and 8-in. diam. mounted directly in front of the lamp house in our special ventilated mount, giving a parallel beam of light in the dark chamber, and the front lens of 4%-m. diam. placed in front of the dark chamber immediately behind the slide carrier. Dark Chamber —Of metal, light-tight, measuring 17x11x8/4 in.; with open- ing in bottom for projected objects, 8 x 10/4 in., and metal diaphragms to give 8, 6 or 4-in. square opening, as desired; provided with two hinged doors giving opening large as entire side of dark chamber; one door has observation window; contains small condensing lens in swinging mount for use in high power microscopical and polariscopical projection. Object Holder —Heavy metal plate, 11/4 x 8/4 in., mounted on double arm with spring hinge at each end and handle at holder end; the whole adjustable for height by quick acting cam actuated by a lever; will accommodate objects of widely varying thicknesses and sizes, the holder always remaining parallel to base and automatically bringing objects into proper plane for projection; metal shield at front of base prevents light from flooding screen when object is being changed, while sliding velvet curtains on either side screen light when large objects are in place. Slide Carrier —Our double, quick changing slide carrier, No. 4449, which gives a semi-dissolving effect and is so arranged that the slides can all be inserted from one side. 80