Born in Paris, France, his most famous inventions are: - the anamorphic widescreen process, using an anamorphic lens system called Hypergonar, that resulted in the CinemaScope widescreen technique, and - the co-invention, with George Willis Ritchey, of the Ritchey–Chrétien telescope, an improved type of astronomical telescope, employing a system now used in virtually all large research telescopes.

He spent part of his early astronomical career at the Nice Observatory, which was close to his house, the Villa Paradou.

The Villa was built by famous French architect Charles Garnier[2][citation needed] who also built the Nice Observatory and both the operas of Paris and Monaco.

In 1995, the abandoned villa was acquired by the artist Rainer Maria Latzke, who restored it and added new murals to the existing frescoes.

Chrétien was one of the founders of the Institut d'optique théorique et appliquée and professor at the French "grande école" SupOptique (École supérieure d'optique).