Abstract
RECENT developments in the design of instruments for the projection of opaque objects have been directed towards increasing the intensity of light directed on the object, improving the quality of the projection lens, and simplifying the mechanical construction in order to ensure lightness, durability, and ease of manipulation. An active part in the development and perfecting of such instruments has been taken by Messrs. Newton and Co. of 72 Wigmore Street, London, W.I. Since the production of their first episcope in 1916, the efficiency and convenience of succeeding models have increased with each stage of development. The high efficiency of their latest types is due largely to the use of special diffusion reflectors. The illuminant is a single 500-watt gas-filled lamp which is so placed that four of these reflectors can be used to concentrate the light on the object and give a uniform illumination over the whole field, an area 6 in. x 6 in. This arrangement, combined with a large aperture projection lens, provides an illumination on the screen equal to that obtained from earlier instruments employing two lamps. As only one lamp is used and the lamp-house well ventilated, the objects are not exposed to any great heat. When it is necessary to keep them at room temperature a ventilating fan can easily be fitted. The silver-surfaced reversing mirror is mounted outside the lamp-house and, consequently, is not subjected to heating from the lamp. The construction of the body, which is of cast aluminium, is such as to ensure lightness and durability; and the design of the instrument renders its operation extremely simple. Precise and easy adjustments are provided for all necessary movements. Instruments of different sizes, embodying these improvements, are available with working distances ranging from 16 ft. to 40 ft.
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Improvements in Epidiascopes. Nature 129, 502 (1932). https://doi.org/10.1038/129502c0
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DOI: https://doi.org/10.1038/129502c0