Home-Made Toys for Girls and Boys/Chapter 21
CHAPTER XXI
A HOME-MADE REFLECTOSCOPE
Fig. 339.—The Complete Reflectoscope.
Fig. 340.—Detail of Ventilator Top.
This reflecting lantern, shown completed in Fig. 339, is more magical in its operation than a magic-lantern is, because, instead of projecting through transparent slides, it reflects opaque pictures. That makes it possible to use magazine and newspaper pictures, post cards, and photograph prints. You may reflect a greatly enlarged picture of the movements of your watch, and by placing your face against the opening in the reflectoscope, you may show a view of your mouth opening and closing, giant size. The ease with which slides are obtained makes this a desirable lantern to own.
Fig. 341.—Plan of Reflectoscope.
The Material. You must get a box about 10 by 10 by 20 inches in size for the case of the reflectoscope, two oil-lamps, or two 16 or 32 candle-power electric lamps with the parts necessary for connecting them to the electric lighting circuit, three 1-lb. baking-powder cans and two tomato cans, two pieces of tin about 6 by 10 inches in size, and a lens from a camera, field glass, opera glass, magic-lantern or bicycle-lamp.
The bottom of the box will be the front of the reflectoscope.
Fig. 342.—Cross-section of Reflectoscope.
Cut Ventilator Holes 3 inches in diameter through the uppermost side of the box, near to the ends and bottom.
Figures 341 and 342 show
The Interior Arrangement of the reflectoscope. Place the lamps in the corners of the box, next to the front, and tack in back of them the pieces of tin for reflectors (A, Figs. 341 and 342). Bend the reflectors to the curve shown.
If Oil Lamps are Used, their tops will project through the ventilation holes, as shown in Fig. 342. These openings must be inclosed with
A Hood which will Conceal the Light, yet allow the heat to escape. The most satisfactory arrangement is that shown in Figs. 339 and 342. A baking-powder can with its bottom removed (B) is slipped over the lamp chimney and fitted into the ventilation hole; then a tomato-can (C) is inverted over the top of the can and fastened in the slotted ends of three wooden peg stilts (D, Fig. 340), and the pegs are fitted into holes made in the top of the box (Figs. 339 and 342). Fasten the can in the slots of the stilts with tacks (Fig. 340).
If Electric Light is Used, the hooded ventilators may be omitted. Any boy who understands the wiring of electric- lamp sockets, plugs, and drop-cord will know how to wire up the reflectoscope.
Mount the Lens in a can or mailing-tube jacket (Fig. 343). If you use a can, remove the bottom. If the lens is smaller in diameter, make a band of cardboard strips to fit around the edge, as shown in Fig. 344, and glue these strips to the inside of the can or mailing-tube. The lens jacket should fit loosely enough in the reflectoscope box opening so it will slide back and forth for focusing. Make a tin collar to fit around the jacket, and tack it to the front of the box, to prevent light from escaping (Fig. 339).
Before putting on the back of the reflectoscope box,
Putty up all Cracks between the boards in the top and front, to make the box light-tight; then
Paint the Inside of the Box and the cover boards with lamp-black thinned with turpentine, so there will be no reflections other than those produced by the lamp reflectors and the picture.
Figs. 343 and 344.—Details of Lens Mounting.
Fig. 345.—View of Back of Reflectoscope.
Fig. 346.—Detail of Post Card Holder.
The Picture Holder, and hinge it in place. A frame for post cards to slide in should be fastened to the picture holder, as shown in Fig. 346. First nail strips F to board E, then tack strips G to them so their edges project over strips F. A little wooden button (H, Fig. 345) will fasten the holder board shut while each picture is being projected.
The Lens Reverses Pictures in projecting them, and in order to have them projected right-side up on the screen it is necessary to slip them into the holder frame upside down.
Adjustments. After you have built your reflectoscope, you may find it does not throw sharply-defined images upon your projection screen. In that case you must readjust the focus of the lens, the curve of the lamp reflectors, and the distance between the lens and the projection screen, until the best possible results are obtained. Inasmuch as the positions will vary with different lenses, it is impossible for me to give any hard and fast measurements. You will have to determine the distances yourself.
The stronger the light, the brighter the projected image will be; therefore, use the strongest light you can get, and place the lantern not more than five feet away from the screen.
Unless you use an anastigmat lens such as the better grade of cameras are fitted with, you will discover that the corners of pictures are indistinct when you have brought the centers to a sharp focus. This indistinctness can be corrected to a great extent by blocking out the holder to curve the post cards and other pictures so that the ends are closer to the lens than the center is.