Hello everyone,
While I have been searching on cartesian oval on the web, I have encountered that Descartes discovered the cross-section curve of the perfect lens, assumed to be a surface of revolution, is a fourth degree curve known today as the cartesian oval. The paper can be reached via the link below:
Here is my question; if the perfect shape of a lens that will focus all rays from one radiant point source to one single image point, and that perfect shape is a surface of revolution with a fourth degree curve; why does ZOS aspheric terms are available more than a fourth degre?
Or otherwise, isn’t a fourth degree surface sufficient to make a perfect focus?
Best regards,