Fundamental Concepts in the Design of the Flying Spot Store

Abstract

The flying spot store is a semipermanent information storage system developed for use in an electronic switching system which utilizes cathode ray tube access to information stored on photographic emulsion. Parallel optical channels are used to provide high capacity and parallel readout. A feedback system provides rapid and precise beam positioning for writing and readout. This paper describes the fundamental design considerations for memory systems of this type, stressing physical realizability, speed, capacity and other system features. The characteristics of a laboratory model are presented.

System Design of the Flying Spot Store

“…In this case, the probability of error depends only on the sampler performance and on the amplitude distributions determined by transmission factors and physical imperfections. In another case, where (1) 370 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1959 the distribution in amplitudes of the incident flux was smaller or where a higher probability of error would be acceptable, some of the total error might be allotted to shot noise fluctuations introduced in the PMT and, in this case, a lower flux level than that of the first example would suffice at the same sampling time. Thus, it is clear that the flux level at the photocathode must be set so that the required electrical signal-tonoise ratio fixed by the system application is obtained in the readout of the most poorly illuminated storage location.…”

Design of a High-Resolution Electrostatic Cathode Ray Tube for the Flying Spot Store

“…A boundary condition is that z = Zo when y = yo. Equation (1) is an integral for which no closed-form solution was found. Fortunately, it is the same as that for space charge spreading in a cylindrical beam, and solutions have been tabulated in generalized graphical form (Ref.…”

“…* The last method was chosen for this work, since experiments showed that the beam cross section in the CRT was substantially Gaussian. Another specification of spot size 1 • 2 is the size of a square that, when centered on the luminescent spot, will contain 90 per cent of the radiant light flux. For a Gaussian spot, the side of such a sq uare is 41T. Flying spot store objectives of large storage capacity and essentially error-free operation result in CRT resolution values of IT = 0.0045 ± 0.00075 inch.…”