Abstract

In proximity focused electrostatic image tube; spatial resolution is a strong function of the cathode flatness. Topographic irregularities of the cathode surface establish transverse electric fields near the cathode. The fields impart a component of transverse momentum to the emitted electron, which, in turn, degrades the spatial resolution characteristic of the system. Calculations based on a simple model of a corrugated cathode show that, under a typical set of operating conditions, the point at which loss of resolution becomes considerable is 60 cycles/mm for a bump height of 0.2 μm and a bump period of 1 μm. For the resolution to be comparable to that predicted for a perfectly flat GaAs negative electron affinity (NEA) cathode, which is 160 cycles/mm, the bump period must be 0.1 μm, and its height must be 0.02 μm. Such small bumps represent a relatively smooth surface. Observations of surface irregularities on related NEA surfaces indicate that the bump period and height are about 1.0 μm and 0.2–0.5 μm, respectively, so that the spatial resolution in these cases is limited by the deviation from flatness as opposed to being limited by the finite random velocities of the emitted photoelectrons.

© 1973 Optical Society of America

Image transfer properties of proximity focused image tubes

Edward H. Eberhardt
Appl. Opt. 16(8) 2127-2133 (1977)

Performance Characteristics of Proximity Focused Ultraviolet Image Converters

Jack T. Williams and Walter A. Feibelman
Appl. Opt. 12(12) 2832-2837 (1973)

MTF of Proximity-Focused Image Tube in Polychromatic Light

O. P. Nijhawan, P. K. Datta, and C. R. Sharma
Appl. Opt. 14(2) 509-512 (1975)

Modulation transfer function of image tube lenses

Illes P. Csorba
Appl. Opt. 16(10) 2647-2650 (1977)

Photomultiplier Single Photon Counting Efficiency

L. Birenbaum and D. B. Scarl
Appl. Opt. 12(3) 519-521 (1973)