From 525/625 TV lines to HDTV, the evolution of optical requirements for TV cameras

Two important requirements make HDTV lenses different from present television lenses. First the picture is wider, and although the image may be scanned over the same sensor diagonal, the 16:9 aspect ratio necessitates better correction of distortion. Secondly the quality of HDTV has to be twice as good; the same MTF must be maintained, although the spatial frequency is doubled. While this level of performance is not new to the optical designer who has already been involved with photography or motion pictures, the task is considerably more difficult because of the following constraints: (1) good camera sensitivity requires high aperture optics; (2) operational requirements dictate long zoom ranges; and (3) a beam-splitting prism is located between the lens and the sensors. This paper explores in some detail what is needed and what can be done in order that the lens does not limit the HDTV system´s performance