History: The Origins of Gratings

In 1785, American scientist David Rittenhouse observed spectra using gratings made with a set of parallel wires. In Germany, however, Joseph von Fraunhofer first measured and identified several spectral lines in the light of the Sun using a prism. His observations in 1814–1815 mark the beginnings of spectroscopy.

Joseph von Fraunhofer (1787–1826)	Fraunhofer’s hand-drawn solar spectrum (bottom), and a photographic solar spectrum

John Barton of London patented a process for making rulings on round, metal discs. His decorative “Barton’s Buttons” were a by-product of his attempts, with Henry Maudslay, to make a perfect screw. Barton later made a grating with 800 lines per centimetre (2,000 lines per inch) for scientist David Brewster, although the ruling diamond broke before the grating was completed. Joseph Saxton made a grating in the U.S. during the early 1840s. It was used by astronomer John W. Draper to make the first photograph of a spectrum, soon after the invention of photography.

Friedrich Nobert (1806–1881) was one of the most talented instrument-makers of the nineteenth century. In his first week at the Technical Institute in Berlin, he learned scale-dividing techniques, and soon made his own dividing engine. Nobert’s interests included testing microscope optics. In 1845, it occurred to him that the technology of dividing engines could be used to engrave microscope test targets on glass. His first “test plate” had line spacings of 440 to 1,760 lines per millimetre (11,000 to 44,000 lines per inch). This was the first target, with known spacing, which could be used to objectively test the quality of microscope optics. By 1873, he had made a test plate with 9,000 lines per millimetre (225,000 lines per inch)!

Nobert made test plates and the best gratings until ca 1870.

Nobert’s ruling engine, made ca 1845–50

Electron micrographs of one of Nobert’s microscope test plates (Courtesy Gerard L'E. Turner)