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interlaced scanning[¦in·tər¦lāst ′skan·iŋ]
a method of television scanning in which the transmitted image on the target of the television camera tube and the television frame on the screen of the picture tube are produced by a single scanning of two frame fields; the odd lines are scanned and reproduced for the first field, and the even lines, which are positioned in the spaces between the lines of the first field, make up the second field. When scanning of the second field has been completed, the beam is returned to the point where the scanning of the first field begins.
Interlaced scanning is used in television systems with an odd number of scanning lines z because only in this case is there a nonintegral number of lines z/2 in each field, so that the beginning of scannings of the first and second fields (and, as a result, the television rasters of these fields) are displaced along the vertical by half the displacement of adjacent lines in a field. It permits a 2:1 reduction in the frame frequency needed for line scanning (since the flicker frequency of the images on the screen is equal to the field frequency) and thereby reduces by half the upper frequency limit of the television signal spectrum.
REFERENCESSee references under TELEVISION.
N. G. DERIUGIN