Claude Mydorge trained as a lawyer but really had little need to work as he came from a wealthy family. He was able to devote most of his life to research in mathematics without having the problems of earning a salary.
Mydorge studied geometry and physics. He published books on optics and conic sections, for example De sectionibus conicis contains a wealth of new examples and ideas which were used by many later geometers. His work simplifies many of Apollonius's proofs.
He was interested in mathematical recreations and edited Récréations Mathématique. Mydorge's book Examen du livre des récréations mathématiques was published in 1630 and later books, such as one by Denis Henrion (1659) were often based on it.
Mydorge left an unpublished manuscript of over 1000 geometric problems and their solutions.
It was not only mathematical problems which interested Mydorge. He also worked on light and refraction in particular. His interest in optics also fitted in with an interest in making astronomical observations. He was a close friend of Descartes and made a large number of optical instruments for him; the two shared a strong interest in explaining vision and the instruments and lenses were to help develop theories.
One of Mydorge's most famous results was an extremely accurate measurement of the latitude of Paris. He was also interested in methods of determining longitude and was appointed to a committee to determine the whether Morin's methods for determining longitude from the Moon's motion was practical. Hérigone and Étienne Pascal served with him on this committee.