Abel Foullon

Their son Benjamin Foullon or Foulon also became a portrait painter and miniaturist.

Foullon invented a holometer, an instrument for making of angular measurements for surveying.

In 1551, Henry II granted Foullon a 10-year exclusive patent monopoly on the holometer in exchange for publishing a description of it.

This first patent specification was entitled "Usage & Description de l'holomètre".

[2] Media related to Abel Foullon at Wikimedia Commons