| 摘要 |
A cathode-ray tube, particularly an index-tube, having a narrow, elongated spot. The electron gun of the tube comprises an astigmatic lens, since its grid has a narrow, elongated opening. In order to avoid S-shaped deformation of the spot upon simultaneous deflection of the electron beam in the horizontal and vertical directions the anode of the electron gun is provided with an opening which widens up in the direction towards the target plate on the side remote from the cathode in planes parallel to a plane going through the axis of the electron gun and the direction of length of the spot produced by the electron beam at the centre of the target plate. The anode opening preferably has an elongated sectional area in planes at right angles to the axis of the electron gun the longitudinal direction of said area intersecting substantially at right angles the direction of length of the grid opening in order to reduce the dependence of the width of the spot upon the beam current.
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