MANUFACTURING PROCEDURE OF A CORRECTING MASK FOR A FOLLOW-UP PICTURE AUTHORISATION HOLDER WITH LONG CATHOD AND APPROACH, AND PROCEDURES FOR CORRECTING A PICTURE AUTHORISATION HOLDER.

摘要

A method is described for manufacturing a correction mask for an image intensifier tube of the proximity-focus type having an oblong cathode and anode. Such image intensifiers tend to have a non-uniform light output at the anode in response to a uniform input image at the cathode. A measurement is made of the light output distribution along at least one line at the anode under uniform illumination of the cathode, which measurement is used to manufacture a transparency for attachment on the output window of the image intensifier tube. The transparency is provided with a light absorbing line, which line absorbs more light at those positions along the length of the output window where the light output was higher. The absorbence of the light absorbing line is made proportional to the difference between the actual light output and required value light output, whereby the light output of the image intensifier tube is equalized to a required level.