What rotating machine did Leonardo da Vinci sketch for grinding lenses accurately?

Leonardo da Vinci sketched a lens-grinding machine for shaping optical lenses accurately.

The design belongs to Leonardo’s broader work on optics, mechanics, and the practical manufacture of scientific instruments. His surviving notebooks contain drawings of machines intended to hold and rotate lenses while an abrasive surface shaped them. This reflects his interest in how vision worked and how lenses could improve observation.

Leonardo did not establish a modern optical factory, and the surviving drawing is a design rather than proof of a completed working machine. It is therefore best described as a proposed lens-grinding machine, not as the invention of the modern camera or telescope.

A related common mix-up is crediting Leonardo with inventing the telescope. He studied light, reflection, refraction, and perspective, but the telescope is generally associated with early seventeenth-century instrument makers, more than a century after his death. His lens machinery shows the practical side of his scientific investigations.