Answers are grounded in this paper and cite their sources.
A family of plane curves is developed which can diffract incident parallel rays to a point focus. These curves, termed diffractoidal curves, are rotated around an axis to produce surfaces of revolution correspondingly termed diffractoids, whose imaging properties for sources at infinity are studied by ray tracing in a few examples. The paraboloid emerges as a limiting case of the diffractoid. A comparison is made between the stigmatic focusing properties of the diffractoid and the toroidal grating.
No takes yet. Share an insight, caveat, or question.
Kastner et al. (1978) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: