An electrostatic image tube with planar photocathode

It has been possible to flatten the electron image of a planar photocathode sufficiently well to obtain images with good center-to-edge focus on a planar screen. The essential element in the new tube is a spherical mesh with strong curvature. This mesh serves the dual function of a prefocusing lens in the approach space, and a field-flattening lens in the image space following. Additional advantages include an incidental correction of pin-cushion geometry and improved high voltage stability. Image resolution of over 16 line pairs/millimeter has been realized with meshes as are available at present. Further progress is entirely possible pending future developments in the technology of high-resolution meshes.