Aberration in Magnetic Focus Systems

Methods are devised for obtaining the point spread function, line spread function and modulation transfer function for magnetically focused image tubes. These are applied to a variety of synthetic electron distribution functions which imitate the behaviour of real photocathodes. These distributions lead to analytical solutions for the intensity in the gaussian image plane, but for other planes numerical methods must be adopted. The maximum possible resolution and depth of focus can then be derived. Other limitations on the resolution are discussed.

Section: Simulation Of Electron Trajectoriesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On the electron optics of magnetically focused image tubes: I. Chromatic aberration in uniform fields

Hartley

1974

“…The RMS (root mean square) chromatic disc radius was shown in Paper I to be smaller by a factor yL1 than the classical figure derived for a maxwellian initial energy distribution by Beurle and Wreathall (1962). More generally, the shape of the point-spread function calculated for any given energy distribution is unaltered except for a scale change by a factor yL1 compared with non-relativistic calculations.…”

Section: 2 Chromatic Aberrationmentioning

confidence: 76%

The electron optics of high-voltage magnetically-focused image converters. II. Aberrations and the effects of transverse fields

Coleman¹

1982

In pt.I (ibid., vol.7, p.1877, 1974) concerning the electron optics of high-voltage image converters using homogeneous coaxial electric and magnetic fields, it was shown that a relativistic treatment leads to a rather small deviation from the 'classical' focus condition. Here, it is shown that aberrations resulting from non-uniformity of the fields, and also image displacements caused by deliberately applied transverse electric or magnetic fields, are reduced by several per cent compared with those calculated using non-relativistic formulae. Methods are presented which enable the results of existing classical treatments to be simply corrected to account for relativistic effects.

“…In I an approximate formula due to Beurle and Wreathall (1962) was used to give the position of a particular electron in the image for some plane. Because the image is no longer circular, the formula must be modified to give x and y , the displacements of the electron from the centre of the image in the radial and transverse directions.…”

Section: The Simulation Of Electron Trajectoriesmentioning

confidence: 99%

On the electron optics of magnetically focused image tubes: III. The effects of non-uniform fields on the resolution

Hartley¹

1974