Effect of self-sharpening in low-velocity electron-beam scanning

In order to clarify the self-sharpening effect which occurs in widely used camera tubes whose operation is based on the low-velocity-beam landing principle, the author has established a two-dimensional and nonlinear analysis. The details of the self-sharpening effect were investigated by developing a calculation program. The fundamental dependence of resolution capability on the following factors was established in terms of the self-sharpening effect: i) the landing characteristics of the scanning electron beam, ii) the specifications and operational conditions of the camera tube target, and iii) the television scanning standards. As a result, it was found that the self-sharpening effect has a great influence upon the resolution of camera tubes and is indispensable for the future design of tubes. Important results obtained include: the amplitude response value for any specified spatial frequency is decreased With the increase in test chart stripe inclination to the vertical direction; the resolution cannot be increased in proportion to the size of the scanned area; among parameters that specify television standards, the number of scanning lines influences the resolution capability the most, and, at the optimum number of lines, frequently encountered astigmatic resolution can be eliminated.