title: Proper and improper stigmatic optical systems.
abstract: Stigmatic optical systems are of two classes: proper and improper stigmatic systems. The purpose of the article is to explore the nature of the two classes. The image may be rotated in the case of proper stigmatic systems and is reflected in a line in the image plane in improper stigmatic systems. Chirality is preserved through proper stigmatic systems but reversed in improper systems. The image also undergoes magnification that is the same in all meridians and, in the case of decentered systems, a transverse translation. Negative magnification implies inversion in a point. The magnification depends on the distance of the object plane from the system, whereas the rotation and reflection do not. The article shows how to identify a system as astigmatic or proper or improper stigmatic from the transference and how to construct the transference of a system that will achieve a particular magnification and rotation or reflection.
authors.affiliation: Optometric Science Research Group, Department of Optometry, Rand Afrikaans University, Johannesburg, South Africa. wfh@na.rau.ac.za
authors.forename: W F
authors.initials: WF
authors.lastname: Harris
mesh_terms: D001251:Astigmatism / Q000503:physiopathology*; D006801:Humans; D008433:Mathematics; D009799:Ocular Physiological Phenomena; D012029:Refraction, Ocular / Q000502:physiology*