STUDY OF TV-TYPE RADIOMETRIC SYSTEMS

摘要

A study was made of the video response of an linage orthicon camera to point source illumination. This study produced some significant experimental and theoretical results which may also be applicable to other TV sensors. Experimental results are presented on the response to a single point source that is fixed or changing in intensity of radiation. The measurements taken with a type GL 5358 image orthicon, having an S10 photocathode and MgO target, indicate the tube has a sensitivity of about 10-13 watts and a dynamic range of 10 (40 db). Experimental results are also presented on the resolution of two point sources and the video response of the two sources when one is changing in intensity or position. For adjacent point sources that differ greatly in intensity the response of the camera was non-linear. The presence of the bright source sometimes completely obliterated the response of the dimmer. The experimental measurements included the effects of variation in point source radiation as well as that of background lighting and TV camera operating parameters. Theoretical results have been obtained on defocusing in the image section of the camera, diffusion of charge on the target, and the trajectory of electrons in the read-out beam current. Preliminary results indicate deflection of electrons by a large point charge on the- target may partially cause both the spreading of response to high intensity signals as well as the disappearance of the weak point source adjacent to a strong one.