Augustin-Jean Fresnel (1788 - 1827) - The Fresnel lenses
Early lifeAugustin-Jean Fresnel was born 10 May 1788 in Broglie, Normandy, France. Augustin was the second of four sons of the architect Jacques Fresnel (1755–1805) and his wife Augustine, née Mérimée (1755–1833). In 1790, following the France Revolution, Broglie became part of the département of Eure. The family moved twice – in 1789/90 to Cherbourg, and in 1794 to his father's home town of Mathieu, where Madame Fresnel would spend 25 years as a widow, outliving two of her sons.
His older brother Louis (1786–1809), was admitted to the École Polytechnique, became a lieutenant in the artillery, and was killed in action at Jaca, Spain, the day before his 23rd birthday. The third, Léonor (1790–1869), followed Augustin into the civil engineering, succeeded him as secretary of the French Lighthouse Commission, and helped to edit his collected works. The fourth, Fulgence Fresnel (1795–1855), became a noted linguist, diplomat, and orientalist, and occasionally assisted Augustin with negotiations. Fulgence died in Bagdad in 1855 having led a mission to explore Babylon. Léonor apparently was the only one of the four who married.
EducationThe Fresnel brothers were initially educated at home by their mother. The ailing Augustin was considered a slow and not too smart learner; but the popular story which he did not begin reading until age eight is disputed. By the age of nine or ten he was unremarkable except for his ability to turn tree branches into toy bows and guns which worked very well, earning him the title of "l'homme de génie" (the man of genius) from his friends.
In 1801 Augustin was sent to the École Centrale in Caen, as companion for his older brother Louis. But Augustin improved his performance. At the end of 1804 he was admitted to the École Polytechnique in Paris, where he placed 17th in the entrance examination. As the detailed accounts of the École Polytechnique begin in 1808, little is known of Augustin's time there, except that he made few if any friends and—despite continued ill health—excelled in drawing and geometry.
He graduated in 1806 and then enrolled at the École Nationale des Ponts et Chaussées (National School of Bridges and Roads, also known as "ENPC" or "École des Ponts"), graduating in 1809. After his exam, he joined the Corps des Ponts et Chaussées as an "Ingénieur ordinaire aspirant" (ordinary engineer in training). Directly or indirectly he would remain in the service of the "Corps des Ponts" for the rest of his life.
Professional careerThe French Commission for Lighthouses was created on April 29, 1811. In 1813, François Arago(1786 - 1853), French mathematician and politician, became a member of this commission. The development of the lighthouses was still in its infancy. An important lack was visibility; this one was very limited.
In 1819, Arago offered the commission to make a systematic review of possible improvements in lighthouse lighting. He asked the committee to assign Augustin Fresnel to the project as his colleague. His request was granted on June 21, 1819, and Augustin agreed to serve on the committee. Augustin produced his first report on lighthouse optics and lamps on August 29, 1819, just two months after he started the project.
Fresnel began his report with a full analysis of the design of the reflectors then in use. He followed with a proposal for the use of glass lenses to replace the metal reflectors, and for the use of a single large Argand-style bulb with concentric wicks to replace the multiple single-wick bulbs required with reflectors.
The first trials of using lenses in lighthouses first took place in England around the end of the 17th century. These tests failed because of the large loss of light due to the thickness and the poor quality of the glass. These lenses also turned out to be unsuitable because they were too heavy. To solve the weight and thickness problems, Fresnel designed a new type of lens (see Fresnel Lenses).
Family liveFresnel battled tuberculosis all his life. In the winter of 1822-1823 his condition worsened, increasing the urgency of his research into lighthouse lights. Treatises on circular and elliptical polarization and optical rotation and their application to internal reflection date from this period. In the spring of 1823 he said he had recovered sufficiently to supervise the installation of the lens in the lighthouse of Cordouan (France).
In 1824 he was told that if he wanted to live longer he had to scale back his activities. Seeing his lighthouse work as his most important task, he resigned as a researcher at the École Polytechnique in Paris. While his basic research stopped, his advocacy didn't stop; it was not until August or September 1826 that he found the time to answer questions from John Herschel about wave theory.
Although he did not become a public celebrity in his lifetime, he lived just long enough to receive much-needed recognition from his peers, including (on his deathbed) the Rumford Medal from the Royal Society of London through the intercession of John Herschel.
Fresnel's cough worsened in the winter of 1826–1827, making him too ill to return to the village Mathieu in the spring. The Académie meeting of April 30, 1827, was the last he attended. At the beginning of June he was taken to Ville-d'Avray, 12 kilometers west of Paris. His mother joined him there. On July 6, Arago arrived to present the Rumford Medal. Fresnel no longer had the strength to thank the Royal Society for the award. He died eight days later on July 14, 1827 (Bastille Day) at the age of 39.
He was buried in the Père Lachaise Cemetery in Paris. The inscription on his tombstone has been partially eroded away; the legible part says, translated, "In memory of Augustin Jean Fresnel, member of the Institute of France". His name has become an integral part of the modern terminology of optics and waves.