Correction of deflection-aberrations by analog computer

For wide-angle deflection (±25°) of microspot tubes (spot size-8 microns), dynamic correction of focal length (DCF) alone is no longer capable of conserving resolution. It is found, however, that complete recovery of ultra-high resolution (3000 lines per inch) is practical by adding dynamic correction of astigmatism (DCA) to DCF. The laws of error distribution on the tube face are found to be quadratic functions of position coordinates
x
and
y
. Dynamic correction thus requires an ideal product generator that obeys the associative law of multiplication out to large amplitudes. A special beam-deflection type of computer tube has been developed. It operates on the principle of deflecting a square beam across a quadrantal target. An analog computer using three of these "roving-square tubes" (RST's) generates all three dynamic corrections as required by DCF and DCA. Photographs of deflected television microimages show the effectiveness of this analog computer in presenting approximately 9000 spot diameters, or 80 million dots, within a 3-inch square.