What machine did Leonardo da Vinci design to cut and polish glass lenses?

Leonardo da Vinci designed a lens-grinding machine to cut and polish glass lenses.

The machine used controlled mechanical motion to shape a lens against an abrasive surface. Producing a useful lens requires a carefully curved surface, and a grinding mechanism can make that work more regular than polishing entirely by hand. Leonardo’s optical studies made lens production relevant to his investigations of vision, light, and perspective.

Leonardo was not inventing the idea of glass lenses themselves. Spectacles and other optical devices already existed in Europe, and later telescope development depended on improvements by many makers. His design belongs to a series of practical machines intended to improve the manufacture and testing of optical components.

The machine should not be confused with a telescope. It was a tool for making lenses, not an optical instrument for viewing distant objects, and there is no evidence that Leonardo built a working telescope from it.