What machine did Leonardo da Vinci design to manufacture convex lenses more efficiently?

Leonardo da Vinci designed a lens-grinding machine to manufacture convex lenses more efficiently.

His notebooks contain designs for machinery that could shape and polish optical glass. The proposed apparatus used controlled mechanical motion to work a lens surface, addressing the difficulty of producing an accurate curve by hand. Leonardo was interested in optics, vision, perspective, and the behavior of light, so lens-making was closely connected to his scientific investigations.

The machine should not be confused with a telescope or microscope. Those are optical instruments that use lenses, whereas a lens-grinding machine is a manufacturing device used to produce them. Leonardo also did not create a working telescope in the modern historical sense. His optical studies were wide-ranging, but many remained drawings, experiments, or theoretical observations rather than finished commercial technologies.

The design illustrates a recurring feature of Leonardo’s engineering: he sought to mechanize skilled manual work and improve precision through repeatable motion.