Modulated On-axis Circular Zone Plates for a Generation of Three-dimensional Focal Curves Bará, Salvador ; Frère, Christian ; Jaroszewicz, Zbigniew ; Kolodziejczyk, Andrzej ; Leseberg, Detlef Abstract Publication: Journal of Modern Optics Pub Date: August 1990 DOI: 10.1080/09500349014551441 Bibcode: 1990JMOp...37.1287B