US3101472_page_9

US3101472 | page 9 | https://thedailydialectics.com/pdfs/wipow/US3101472/US3101472.pdf

3,101,472 11 for producing a free electromagnetic wave beam with substantially planar wave fronts progressing into a pre- determined direction, having at a predetermined point along its path a substantially uniform cross-sectional phase distribution, phase-correcting means arranged across said path…