What machine did Leonardo da Vinci design to grind lenses with controlled mechanical motion?

Leonardo da Vinci designed a lens-grinding machine to shape optical lenses with controlled mechanical motion.

His notebooks include studies of optics and mechanisms for working curved transparent surfaces. A lens-grinding machine could make the repeated movement needed to polish a lens more consistently than hand work alone.

Leonardo’s optical investigations covered vision, light, reflection, and the anatomy of the eye. These studies did not amount to the invention of the telescope, which is generally associated with Dutch spectacle makers in the early seventeenth century.

The machine is therefore best understood as an optical workshop device rather than a complete viewing instrument. Leonardo left many mechanical proposals on paper, and surviving evidence does not show that every illustrated machine was built or used in a finished form.