Jules Lisajous, French physicist, mid 19th century.
© Science Museum / Science & Society Picture Library
Jules Lisajous (1822-1880) invented the vibration microscope, an optical method for studying vibrations in 1855. He achieved this by attaching a light beam to the vibrating objects that then reflected onto a screen. During the siege of Paris in 1871 Lisajous's system of optical telegraphy was used.