GB654413A - Improvements in or relating to electronic view-finders for television cameras - Google Patents

Abstract

654,413. Television. ELECTRIC & MUSICAL INDUSTRIES, Ltd. Feb. 13, 1948, No. 4217. Drawings to Specification. [Class 40 (iii)] In an arrangement comprising an electronic view-finder fed with picture signals generated in a television camera, the area of the scanned patch in the camera is made larger than the area from which picture signals are derived and transmitted, and the signals derived from the larger area are fed to the view-finder so that it reproduces a picture which extends beyond the limits of the picture transmitted. According to another feature of the invention the additional area which becomes available in the view-finder may be utilized to display instructions transmitted to the camera operator, these instructions appearing either alone or superimposed on picture signals reproduced in the additional area. The increased area is made available by reducing the fly-back time and making corresponding increases to the sweep time of the scanning waves applied to the camera and viewfinder. The picture signals are, however, only transmitted for the normal time, and to cause the added area to appear as a border surrounding the transmitted picture, the synchronizing pulses for the camera and viewfinder scans are delayed with respect to the transmitted picture synchronizing pulses. The beginning and end of the scans may be accelerated so as to increase further the additional area of scan visible in the viewfinder. Due to the acceleration, the added area is less bright and the view-finder displays a bright centre patch corresponding to the transmitted picture surrounded by a less bright border of the surrounding scene. A border line around the transmitted picture may be produced by differentiating the suppression pulses corresponding to the transmitted signal and mixing the resultant pulses with the signals fed to the viewfinder.