(photocomposing machine), a typesetting machine in which the letters and symbols of a text are photographically reproduced on a light-sensitive material—photographic film or paper. The text diapositives or negatives produced are used to prepare printing plates (see). The most commonly used types of phototypesetting machines differ in design, technical capabilities, output, and operating principles; they include manual phototypesetters, automatic systems based on casting machines, functional phototypesetters, and electronic phototypesetters with cathode-ray tubes.
In manual phototypesetters, such as the SFK unit manufactured in the USSR, characters from the type carrier (usually plates with negative images of letters and symbols) are composed by hand and placed in a composing stick to be photographed line by line. Such units are used for composing short texts, such as headlines and names on maps. In automatic systems based on casting machines, the casting devices are replaced by photographic devices, and the matrices are replaced by photomats; the operating principle is the same as that of a casting machine. Such systems photograph at rates up to eight characters per second. Automatic phototypesetters include the Fotosetter system (USA), based on the Linotype and used for uncomplicated texts, and the Monophoto (Great Britain), which is based on the Monotype and makes it possible to compose more complicated texts.
Functional phototypesetting machines are used for composing both simple and complicated texts and are capable of photographing at rates up to 100 characters per second. Such machines include the FA–500 (USSR), Photon (Great Britain), and Europa-Linofilm (Federal Republic of Germany). The systems consist of a control unit and a phototypesetting device. A specialized computer uses a specific program to process signals that control the operation of the phototypesetting device; the latter photographs the text characters from a rotating or other form of type carrier, character by character. Figure 1 shows the optical format of the Photon phototypesetting machine, in which the light beam from a flash lamp located within the type carrier (film matrix) drum traverses the image of the required character, passes through the optical system, and projects the image of the character onto photographic film or paper.
The operation of electronic phototypesetting systems equipped with cathode-ray tubes is based on the reproduction of individual characters, lines, or entire pages on the screen of a cathode-ray tube with subsequent projection onto photographic film or paper. Such systems may feature physical type carriers, such as the Linotron (Great Britain), or they may be equipped with an electronic memory in which the images of characters and illustrations are encoded in digital form, such as the Digiset (Federal Republic of Germany). The latter feature a wide assortment of typefaces and can photograph at speeds greater than 1,000 characters per second. The system may be controlled by a program written on perforated or magnetic tape or by computer. Electronic phototypesetting systems are used for printing large texts in large-scale printing plants or phototypesetting centers.
Phototypesetting machines are now widely used. In comparison with hot metal composition, they often can process texts much faster, offer higher quality reproduction, and greatly reduce the use of expensive alloy type metals. Phototypesetting machines are used in the production of printing plates for offset, gravure, and letterpress printing.
REFERENCESMolin, A. la. Fotonabor. Moscow, 1972.
Petrokas, L. V., and L. A. Shneerov. Mashiny nabornogo proizvodstva, Moscow, 1973.
N. N. POLIANSKII