astigmatic foci

astigmatic foci

[¦a·stig‚mad·ik ′fō‚sī]
(optics)
The two lines on which rays emanating from a point are focused by an astigmatic optical system. Also known as focal lines.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.