POINT SUR STATE HISTORIC PARK

FRESNEL Presented by: Al Friedrich March 22, 2016

Good evening, We are here tonight to talk about Fresnel Lens.

1 Pharos at Alexandria

I was built around 280 BCE on the Island of Pharos itn the harbor of Alexandria, Egypt. In ancient times, visitors could buy food at the observation platform on the first level. Anyone who wished to do could climb nearly to the top. There were not many places in the ancient world that visitors could climb a man-made structure, 400-450 feet up, to view the sea.

2 Open Flame – 97 % of light lost

• Tests showed that an open flame lost nearly 97% of its light.

3 Catoptric Optic - 1784

A Rotating Reflector–Lamp Driven by a Clockwork

In 1784 the catoptric optic, a rotating reflector-lamp system driven by a clockwork weight system, was developed. This mechanism turned the reflectors back and forth creating a unique light source or a change between light and dark, rather than simply producing a constant light. This system was developed due to the need to distinguish the lighthouse beam from others light sources. There is some disagreement as to who was the first to place parabolic reflectors behind Argand‘s 4 Abbie Burgess – Maine 1853

• Abbie Burgess lived on Martinicus Rock on the Coast of Maine in 1853. On January 19, 1856, Capt. Burgess left the Rock for medical, fuel and other supplies. Due to a major storm, he returned four weeks later. Abbie kept the lights burning. Later on in life, she became a . • You can see from the picture that she was cleaning a Catoptric Optic even at this late date. 5 Reflector – 61% of Light Lost

• Tests showed that a flame with reflectors behind it lost more than 61% of its light.

6 Augustin Jean Fresnel

1788-1827 In 1811, Napoleon Bonaparte formed the first national lighthouse organization, the Commission des Phares. The Commission accomplished little in its early years, however, one story alone had dominated the newspapers in 1817, the terrible fate of the passengers and crew on Le Meduse. The Captain abandoned the survivors on a raft when the Captain’s boat cut the towrope to the raft. Some on the raft made it to land to tell of the disaster 7 Augustin Jean Fresnel Con’t

1788-1827

In 1819, it turned its attention to the dismal state of France’s coastline and one of its members, the physicist François Arago, saw the opportunity to bring one of his protégés, Augustin Fresnel, to Paris. The French Government commissioned him to develop an improved lighting system for French . As physicist. He was well known for his experimentation with the theories of light reflection and .

8 Augustin Jean Fresnel Con’t

1788-1827

Ignoring the reflector paradigm, Fresnel instead began investigating ways that glass could be used to concentrate the light source. Since a single lens of sufficient strength would be too large to be practical, Fresnel began looking at ways that multiple lenses surrounding the light source could capture the light rays emitted from a single light source and direct them into a narrow horizontal beam.

9 Biconvex Lens –Lost more light than Reflectors

A lighthouse wants to collect as much light as possible (large diameter lens) and send it out in a beam. This means the lens must have a short (thick lens), so it can be placed close to the light source.

• A lighthouse must send a long beam of light far out to sea. To do that a very large and heavy lens would normally be needed. In 1879, the had several biconvex lenses installed around the side of the lantern room. Five and one-half inches thick, the lenses lost more light than the reflector. Colorado. 10 edu Fresnel Lens Reduces Lens Weight Fresnel had the idea that because refraction occurs at the curved surface, the rest of the glass is unnecessary. If you remove the non-essential glass and flatten the remaining glass segments, you get a Fresnel lens.

•G.-L.-L. Buffon (1748) first had the idea of dividing a lens surface into concentric rings to reduce the weight. In 1820, for the construction of lighthouse lenses. Fresnel had the idea that because refraction occurs at the curved surface, the rest of the glass is unnecessary. If you remove the non-essential glass and flatten the remaining glass segments, you get a Fresnel lens. Fresnel lenses have the optical properties of much thicker and heavier lenses. Colorado. 11 edu The Lens Works in Both Directions

Light Collimation of a Point Source with a Fresnel Lens

Light Collection of Collimated Light with a Fresnel Lens

• APPLICATION EXAMPLES •Augustin-Jean Fresnel (1788 - 1827) was not the first to conceptualize a Fresnel lens, he was able to popularize it by integrating it into lighthouses. Fresnel lenses have been utilized in a variety of applications, from light collimation and light collection to magnification. • Light Collimation – light Collection • Light Collection – Light Magnification

12 First Working Prototype Worked

Fresnel Experimental Lens Prototype - 1821

•The Lighthouse Commission was skeptical, Fresnel built a model to demonstrate its effectiveness. Working with the noted instrument maker François Soleil, he completed a prototype panel by April, 1821. he invited the Lighthouse Commission, and sailors, to witness the trial. Seated high on the hill of Montmartre, they saw the lens far outshine the parabolic reflectors..

cordou 13 an Fresnel Lens - 1822

This section diagram shows how a Fresnel lens (A) in a lighthouse works to collimate light from an oil lamp (L) into a parallel beam. Fresnel increased the light projecting power of lighthouses greatly without the weight of a conventional lens of its size. He also used mirror strips (m,n) mounted above and below the lens that most lighthouses had, to gather more of the lamp's light. Daily 14 Kos Fresnel Lens - 1823

The first lens installed in the Cordouan Lighthouse by Augustin Fresnel. The Lighthouse Commission ordered a full lens to be placed in France’s most illustrious lighthouse, La Cordouan. Lit in 1823, the new lens was a triumph, drawing the attention of sailors from around the world. France immediately embarked on a massive project to blanket the entire coastline in Fresnel lenses At the center the lens was shaped like a magnifying glass, so the concentrated beam was even more powerful. Because of its amazing efficiency, a fresnel lens could easily throw its light 20 or more miles to the horizon. cordou 15 an Fresnel Lens - 1827

Fresnel Lens Bend = Dioptric Bend & Reflect = Catadioptric Prism

This is an example of a plain first-order (non-flashing) lens. The plain curved surface of the lens indicates a constant light.

terrypep 16 per Fresnel Lens – Only 20% Light Lost

The fresnel lens was able to capture all but 20% of its light.

terrypep 17 per Fresnel Lens – Used Today

Truck Tail Light Theater Lantern

• Theatre usage employs a Lens to wash light over an area of the stage. The lens produces a wider, soft-edged beam of light, which is commonly used for back light and top light. • Transpertation applications include (1) passenger reading lights on Airbus aircraft: in a dark cabin, the focused beam of light does not dazzle neighboring passengers and (2) Tail Lights on Trucks and Automobiles.

18 Fresnel Lens Sizes

Order First Second Third 3.5 4th 5th 6th Height 7’10” 6’1” 4’8” 3’0” 2’4” 1’8” 1’5” Focal 920 750 500 375 250 182.5 50 Lenght

Miles: 22-25 20 18 17 15 10 5

Order of Lens Typical Usage First Largest of Seacoast lights Second & Great Lakes & Seacoast Lights Third Seacoast, Great Lakes, Bays & River Entrance Lights Third & Mainly Designed for use on the Fourth Great Lakes Reefs, Harbor and Shoal Lights Fifth Breakwaters, Channel Markers, and Lights Marking Small Islands Sixth Pier and Breakwater lights 19 Point Sur Light - 1889

1st Order Fresnel Lens Flashing – 15 seconds

1889 – Red & White 1925 – White

•A first-order Fresnel lens, manufactured in 1887 by Barbier & Fenestre of Paris, was shipped around Cape Horn. The 4,330-pound lens was then assembled in the lantern room, where a kerosene lantern illuminated it on August 1, 1889. A 450- pound weight was suspended beneath the lens, and after being cranked up by the keeper, it would rotate the lens for four hours. The lens was almost 9 feet (3 m) tall and consisted of 580 separate glass . The entire structure, including the pedestal and clockworks was 18 feet (5 m) tall and weighed 9,570 pounds (4,341 kg).

20 Rotating Powered by Weight

Initially, rotating lens were powered by a clockwork mechanism which was driven by a descending weight. It was designed last a four Watch or shift. Note the small brass wheels known as “Chariot Wheels” on the Point Sur Light. Currently, the original first-order Fresnel lens along with the clockworks are on display at the Museum of Monterey in nearby Monterey, California

21 Fresnel Lens

The moving spokes of light created by the Fresnel lens are very beautiful. The lens throws beams in 24 directions, and the entire lens slowly rotates. Pt. Sur beams in 16 directions.

22 Point Pinos Light – 1855

Point Pinos Light - 1855 3rd Order Fresnel Lens Fixed - Occulting

An occulting light is a lighthouse is a light that operates in a rhythm characterized by periods of darkness of the same length. Occulting lights were invented in 1890 by David Porter Heap, who was known as the “Great Improver” of the US Lighthouse Service due to his many inventions.

cordou 23 an Point Sur Light – 1889 to 1911

Kerosene Wick Lamp

The popular kerosene lamps in the 1890's used round wicks. They were constructed on the Argand principle of supplying air to the flame through a central draft tube. The round wick provided a larger burning surface and gave more light but consumed more oil than the common flat wick lamp. despite, a yellow flickering flame these lamps were an improvement. Point Sur had an oil wick lamp from 1889-1911. cordou 24 an Point Sur Light – 1911 to 1939

Thomas Henderson

Incandescent Oil Vapor Lamp

In 1901, Arthur Kitson, an American, invented a burner in which the oil was converted into vapor under pressure in a retort and then mixed with air in a mixing chamber to form a gas for heating a mantle made of platinum gauze (Similar to Coleman lanterns). {The Incandescent Oil Vapor (I.O.V.) Lamp used air pressure and a fuel vaporizer tube where the kerosene was preheated into a fine gas vapor before it was ignited as a flame.} This dramatically increased the oxygen at the flame and provided a brighter flame using less fuel. Finally in 1921, David Hood further improved and simplified the Kitson burner. PG 25 Museum Point Sur Light – 1939 to 1975

Electric Incandescent 1,000 Watt Bulb

• The unit contains a bulb changing mechanism which holds two electric incandescent 1,000 watt lamps.

seguinisl 26 and Heaven Descended to Earth

• The project to light France’s coast took nearly twenty years to complete. The lighting of Baleines on January 15, 1854, was the final lighthouse completing Fresnel and Rossel’s 1825 plan. Unfortunately Fresnel and Rossel died in 1827 and 1829 respectively and did not live to see the completion of their great work. In our era of GPS, Fresnel lenses offer comfort to those making landfall and the coastwise sailor. France’s premier historian, Jules Michelet, praised the tight network of overlapping rays for its enlightened design. “For the sailor who steers by the stars, it was as if another heaven had descended to earth.” 27 Fresnel Lens Acceptance

Trinity House & Northern Lighthouse Board stuck in reflector mindset (1822-1850) Robert Stevenson skeptical of merits of Fresnel lens over reflectors, but Alan Stevenson accepted Fresnel lens over reflectors.

Between 1790 and 1940, eight members of the Stevenson family planned, designed and constructed the 97 manned lighthouses which still speckle the Scottish coast, working in conditions and places which would be daunting even for modern engineers. The Lighthouse Stevenson's, as they became known, were also responsible for a slew of inventions in both construction and As well as lighthouses, they built harbors, roads, railways, docks and canals all over Scotland and beyond; they, as much as anyone, are responsible for their country’s appearance today.

28 Fresnel Lens Acceptance

In 1812, Stephen Pleasonton, the Fifth Auditor of the Treasury purchased a patented "reflecting and magnifying lantern" from Winslow Lewis, a former ship Captain. Lamp installed in all US Lighthouses prior to 1852.

•In reality, Lewis' "invention" was nothing more than a poorly modified version of the Argand-style lamp. Lewis' lights were also severely flawed: •their reflectors were more spherical than parabolic, •the thin copper that warped when exposed to heat •the silver plating rubbed off easily during cleaning, •the components often fell apart. •Despite such problems, Lewis' lamps were quickly adopted by Pleasonton as the de facto standard, and were subsequently installed in all US Lighthouses prior to 1852

terrypep 29 per Fresnel Lens & Lighthouse Links

beachbum.homestead.com colorado.edu (Ellen Ch. 3 – Mirrors and Lenses) cordouan.culture.fr/accessible/ dailykos.com fresneltech.com/pdf/FresnelLenses.pdf lighthousefriends.com newenglandlighthouses.net photographers-resource.co.uk seguinisland.com terrypepper.com/lights/index.htm themes.pppst.com/lighthouses.html trinityhouse.co.uk

30 The Light is On

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