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a device for the viewing and reading of enlarged optical images of microfilms or microphotocopies. A reader is a projector in which the image of a microfilm frame is projected, by means of an objective and a system of mirrors, on a screen that is built into the device or on an external screen. Depending on the principle of their operation, readers are divided into devices for viewing microfilms and microphotocopies in transmitted light or in reflected light. The most widely used readers are table models, which make it possible to view both microfilms and microphotocopies—for example, microcards or microfiches—on either a transparent or an opaque substrate.
According to their design, readers are divided into devices with a diffusely reflecting screen and devices with a translucent screen. The components of a reader with a diffusely reflecting screen may include a mirror attachment for projecting images on an external screen.
In a reader with a diffusely reflecting screen, light from an electric lamp passes through a heat filter and a system of lenses and falls on a microfilm frame. The optical image of the microfilm frame is projected, by means of an objective and a mirror, on a screen located within a housing that shields the screen from light. Such a housing makes it possible to use the reader in undarkened rooms.
In a reader with a translucent screen, rays of light pass through a heat filter and fall on a microfilm frame. The image of the microfilm frame is projected on the translucent screen by means of an objective and a system of mirrors.
In working with microphotocopies, it often becomes necessary to obtain an enlarged duplicate of a document. For this purpose, a reader copier is used. In such a device, a reader and a reprographic system are integrated. The first reader-copiers, which were manufactured by Kodak (USA) in the 1930’s, made copies on photographic paper. In present-day reader-copiers, enlarged copies are produced on dielectric paper or on ordinary paper by means of electrography. Work with reader-copiers is carried out in two stages. First, the required microfilm frame is retrieved on the screen; then, an enlarged copy is produced.
Readers and reader-copiers are office equipment. They are used in libraries, in the scientific and technical information departments of scientific research institutes, in design organizations, and in other organizations where the type of activity requires microfilming.
REFERENCESSee references under MICROFILMING.
A. IA. MANTSEN