The Remarkable Fresnel Lens

Fresnel Lens, Vashon Island, WA, 5th Order

A modern invention of the 1820s that revolutionized the science of light and shipping was the Fresnel lens. This invention, created by Augustin-Jean Fresnel (1788-1827), is a lens with an array of prisms capturing light and extending its reach. Today we are still influenced by these lenses around the world.

 

Fresnel (pronounced fray-NEL) lenses were originally created as a solution for the tragic ship wrecks that were prevalent in the 1800s. Ship captains, sometimes unable to see coastal waters due to low light, crashed their vessels into the reef with disastrous results.

 

Light naturally diffuses in all directions. Finding a way to cut down on this diffusion was the challenge for many years. At the time, shiny metal reflectors around the light source (oil lamps) were used to enhance the light, but this only gave about 50% reflection.

 

French physicist Augustin Fresnel’s skill and brilliance in interpreting the mechanics of light led to innovative lens inventions. Lighthouse visibility improved tremendously, and consequently made shipping safer.

 

Although I have been to many lighthouses, I never regarded the light as anything special. Then last year I was in the Visitor Center at a California State Park, Angel Island, and became instantly dazzled by a waist-high glass piece mounted on the floor. It had once been used in the lighthouse on Angel Island, and was on display.

 

It captured the light of the room in the most extraordinary, and beautiful, way. I’ve been a fan ever since.

 

Vashon Island, WA Lighthouse. You can see the Fresnel lens in the tower through the windows.

There are numerous aspects that make the Fresnel lens unique and effective:

  • the beehive-shaped design to capture multiple levels of light
  • it is constructed with concentric grooves that act as individual refracting surfaces.
  • the center is shaped like a magnifying glass, concentrating the beam

 

The first lens was installed in 1823 off the west coast of Fresnel’s home country, France, near Brittany, a land long-known for its rugged coasts. Here there were treacherous reefs that tragically and repeatedly snagged and destroyed ships. The new lens was a success.

 

Thereafter the French coast was lit up by Fresnel lenses. More info: Cordouan Lighthouse.

 

Early innovations began in France and Scotland, with America and other countries following. Chronology of Fresnel Lens Development.

 

Fresnel lens, Vashon Island, WA. Mt. Rainier in distance

Each lens was produced in brass-framed sections and could be shipped unassembled from the factory.

 

They were made in six different classifications, or orders. A 1st order lens is the largest size, at approximately 12 feet high (3.7 m), lengthening the light beam 26 miles.

 

Wikipedia Fresnel Lens

 

Here is a cross section of the Fresnel lens (on left) compared to a conventional lens of equivalent power (on right).

1 Cross section of a spherical Fresnel len, 2 Cross section of a conventional spherical lens

Courtesy Wikipedia

 

Article:  “The Fresnel Lens” written by Thomas Tag

 

Lighthouse Science: Why the Fresnel Lens Costs a Million Dollars

Fresnel Lens classifications. Courtesy partsolutions.com

 

Lighthouse beacons have been  significantly modernized since the 1800s, but there are still lighthouses with Fresnel lenses–some in working order, some just on display. There are also many Fresnel light-refracting techniques in use today: spotlights, floodlights, railroad and traffic signals, camera and projector lenses and screens, and emergency vehicle lights.

 

List of U.S. lighthouses with Fresnel lenses

 

Many photographers and artists, including myself, hold a deep fascination and reverence for the miracle of light. How fortunate for us to have had Fresnel’s engineering skills to brighten this further.

 

Written by Jet Eliot.
Photo credit: Athena Alexander unless otherwise specified.

 

Rotating Fresnel lens, 1st order, dated 1870, displayed at the Musée national de la Marine, Paris. Courtesy Wikipedia.

 

1st Order Fresnel lens, Cape Meares Lighthouse, Tillamook, OR, USA. Courtesy Wikipedia.

 

 

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Cable Cars – A San Francisco Treat

Hyde-Powell Cable Car track

Beneath the streets of San Francisco are underground cables that run all day long. If you can catch a quiet moment on one of the cable car streets, you will hear the high-pitched hum of the constantly running cable.

 

Originally invented by Andrew Smith Hallidie, cable cars have been carrying commuters and tourists through San Francisco since 1873. Designated a U.S. National Historic Landmark, it is the only true cable car system left in the world.

San Francisco cable car, California Line

Cable Car Wikipedia

 

This network of cables and pulleys originates from one powerhouse located at Washington and Jackson Streets, and it runs the whole city’s cable car system. Here there is also the Cable Car Museum, which I recommend; it’s free.

Cable Car Museum. Underground cables operating in powerhouse

Each cable car has two operators: the conductor, who takes tickets ($7.00); and the grip person, who runs the car and grips the brakes.

 

With the underground cable running, the grip person starts and stops the cable car by attaching to or releasing from the cable. This takes great strength; the car has a passenger capacity of 60-68 people. So one Herculean person operates the grip that brakes the car carrying 60+ people.

 

Cable car grip man

 

 

Cable car stop

 

San Francisco Hyde Street cable car

The history and facts are interesting…but it’s the ride that is the thrill.

 

I have lived in or around San Francisco for 30 years, and I never ever tire of riding the cable cars.

San Francisco cable car

The wind is blowing through your hair, the car is rocking slightly, and creaking. The car is sandwiched between UPS delivery trucks, other double-parked work trucks, and speedy cars as we trundle up and down the precipitous hills.

 

Street scenes abound as we cruise by apartment buildings, houses, corner stores, and schools.

 

The clanking of the bell, the dampness of the fog.

 

From a few of the hilltops you can see Alcatraz Island in the distance, anchored in the Bay; and the Golden Gate Bridge. The aroma of savory foods waft out of Chinatown.

 

A quintessential San Francisco experience…not to be missed.

 

Written by Jet Eliot.

Photos by Athena Alexander.

Cable car riders. From R Athena, Jet, Jet’s sister, and brother-in-law. July 2018.

Check out this old cable car commercial from 1962, pretty fun.

 

Camera Obscura, San Francisco

Camera Obscura, San Francisco

Of all the beautiful spots to visit in San Francisco, this is one of my favorites. A giant walk-in camera taking 360-degree real-time images of the sea. For a $2.00 entry fee, we are given the gifts of seaside panorama and peace.

 

Named Camera Obscura, for the Latin translation “dark room,” it operates on the photographic “pinhole image” concept that dates back centuries, based on a natural optical phenomenon.

 

Rays of light travel in a straight line, a law of optics. When rays of bright light pass through a small opening, like a pinhole, they reappear reversed and inverted. By using a dark room, two lenses, a mirror, and a surface, the images turn right-side up and appear before you.

 

The small building is perched above Ocean Beach in San Francisco, overlooking the Pacific Ocean. It is on the register of National Historic Places.

Front view.

The mirror is in the triangle at the top, lenses below it, and the turret rotates.

 

San Francisco’s Camera Obscura website:  giantcamera.com

Wikipedia Camera Obscura information

 

 

Image on screen inside the Camera Obscura

The concept of capturing light into images, like the Camera Obscura, is similar to the human eye. From Wiki: “The human eye … works much like a camera obscura with an opening (pupil), a biconvex lens and a surface where the image is formed (retina).”

 

The oldest mention of this phenomenon dates back to 5th Century China.

Pinhole-camera.svg

Camera Obscura Effect. Courtesy Wikipedia

In the 16th century, philosophers, scientists, astronomers, and artists used the light tool for viewing eclipses, studying light, and even drawing. Before mirrors and lenses, they simply used the light and the pinhole. It was a fascinating topic of interest for scholars, and interpreted as an invention of the devil for others.

Diagram courtesy Camera Obscura, San Franciso

By the 18th century, the Camera Obscura had gained popularity for education and entertainment. Often parks or scenic spots had one, like New York City’s Central Park, and also Coney Island. Old Camera Obscuras that no longer exist. Just as it was used for science, art, and entertainment; it was also used for training in wars.

 

Camera Obscuras are the first cameras. Photography pioneers like Fox Talbot, Niepce, and Daguerre created cameras by modifying Camera Obscuras. Soon after, when light-sensitive plates and film were invented, the Camera Obscura was no longer necessary.

Ocean Beach

Ocean waves on screen

 

Today there are Camera Obscuras in the U.S., England, Scotland, Wales, and other countries. Some are old, some are new. There are private Camera Obscuras and public ones; less than ten public ones exist in the U.S. The Wikipedia link provides all locations.

 

This one in San Francisco was built by Floyd Jennings in 1946 for a popular amusement park in the 1900s, Playland at the Beach. When Playland closed in 1972, the structure was relocated to its present location, behind the Cliff House at Ocean Beach.

 

For those of us who can never get enough of Camera Obscuras, a good website to feed your fix is brought to us by Jack and Beverly Wilgus, scholars of this phenomenon:  Magic Mirror of Life

 

You might wonder, why would this be anything great these days when you have a phone in your pocket that takes excellent photos? Or easy-access live cams? Or why would you go inside a building when you have the whole outdoor image in full view?

 

Because with the Camera Obscura, you are in the camera. Inside the camera.

Outside it is noisy from the wind and the crashing waves, and sometimes blindingly bright from the vast, open sea.

 

You walk through the curious saloon-style doors and enter a world of magic. At first you can’t see anything, going from the brightness of day to darkness.

 

But then your eyes quickly adjust, and your body relaxes in the darkness and peace. You’re in a special little cocoon.

 

On the screen before you are the ocean waves silently lapping against the beach. Surfers in wet suits, dogs and dog owners walking the beach, cars moving down the Great Highway. The image slowly rotates, constantly changing, just like life…only softer and gentler.

 

Way out in the distance are ships sailing the sea. Closer in are large boulders covered with cormorants and gulls.

 

In that dark and hushed room you enjoy a few magical moments of gentle light and silence, and see the profoundness of life as it is unfolds.

 

Photo credit: As indicated

Video clip on San Francisco’s Camera Obscura

 

Camera Obscura, San Francisco

 

Visiting Alcatraz

Alcatraz Island

Alcatraz Island

Alcatraz Island is the most visited attraction in San Francisco, entertaining over 1.3 million visitors every year. The Los Angeles Times declared it the seventh most popular landmark in the world (06.16.15).

 

Every day one boat after another leaves Pier 33 loaded with Alcatraz-bound tourists who are curious to visit the famous prison, learn the notorious history. As a San Francisco resident I had already visited here, then returned one day in 2014 to study the setting for a scene in my novel.

 

How Alcatraz began. After gold was discovered in California in 1848, prospectors, businessmen, and families arrived here in droves. It was determined then that the increased value–millions of dollars worth of mined gold–created a need for defense and protection.

Alcatraz dock

Alcatraz dock

Thereafter it became a:

  1. Fortress and military installation (1853-1933) ;
  2. Federal Penitentiary (1933-1963)
  3. Native American protest occupation (1964, 1969-1971)
  4. U.S. National Park (1972-present)
Alcatraz cell block

Alcatraz cell block

Read more history, overview here.

 

Touring “The Rock” requires  reservations and involves a fun ten-minute boat ride on the San Francisco Bay.

 

More about touring here.

 

 

Visitors take a self-guided tour with audio tapes narrated by prison guards. You can stay at the island all day until the last boat departure, but most people stay a few hours.

 

Alcatraz cell

Alcatraz cell

In addition to being a tourist prison island, Alcatraz (the Spanish word for “pelican”) is also a prominent site for nesting birds; and has tide pools, sea mammals and other wildlife, even glowing millipedes.

 

The day we were there we saw Anna’s hummingbirds, a variety of sparrows, plenty of gulls and cormorants.

 

National Park Service nature info here.

Glowing millipedes on Alcatraz here.

 

The boat drops you off at the dock, a ranger gives you an overview of the facility and the rules. There’s a steep walk up to the prison, passing by old military gunnery, the water tower and guard towers, other old buildings, and gardens.

 

Alcatraz scaled model at Pier 33, Jet (in pink)scoping it out

Alcatraz scaled model at Pier 33. Jet (in sunglasses) scoping it out.

All the photos here are from that October day when I went to observe and take notes. Golden Gate Graveyard readers will recognize some of these sights from the Alcatraz scene.

 

Once you get up to the cell blocks, you can walk around inside the prison, see where prisoners showered, slept, and ate. Outside you view the warden’s half-burned house, the lighthouse, beautiful views of San Francisco and other sites.

 

Angel Island from Alcatraz

Angel Island from Alcatraz

Having written and researched a lot of history about San Francisco for this novel, I find two things especially fascinating:  over the years once-serious facilities, like Alcatraz, have turned into frolicking tourist attractions. And how curious it is to witness visitors’ intrigue and animation at this decrepit and defunct old prison.

 

The prison has been extensively featured in books (ahem), films, video games, TV series, and more. A popular new Alcatraz-related attraction is the Escape Alcatraz Drop Ride at the San Francisco Dungeon. It is a stomach-dropping ride simulating an attempted escape.

 

Alcatraz Control Room

Alcatraz Control Room

All modern-day Alcatraz folklore stems from the inescapability of this maximum security prison. It was long touted as the place from which no man ever left alive.

 

But is that true? Over 50 years after three prisoners escaped and their bodies were never found, there is still speculation and “Search for the Truth” documentaries. I recently watched a 1979 film starring Clint Eastwood called “Escape from Alcatraz.” It’s pretty good, shows life on The Rock and is based on the actual escape.

 

For an old prison that hasn’t seen a prisoner in over half a century, Alcatraz sure is a lively place. I’m happy it makes for good fiction.

 

Alcatraz view of San Francisco

Alcatraz view of San Francisco

 

 

Photo credit: Athena Alexander

 

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The Mission Dolores Cemetery, San Francisco

Mission Dolores, San Francisco

Mission Dolores, San Francisco

The oldest building in San Francisco, the Mission San Francisco de Asis, more commonly known as Mission Dolores, was built in San Francisco in 1776.

 

In the back, behind a white adobe wall, is the old cemetery. It is one of the quietest spots in this urban sprawl.

 

Between 1769 and 1833, 21 Spanish missions  were established by Franciscan priests throughout what was later to become the state of California. The sixth mission to be founded was the San Francisco one. The missions were the origins of the state’s communities.

 

Mission San Francisco De Asís

Old Mission on left, Basilica on right. Photo: Robert A. Estremo, courtesy Wikipedia.

More information about the missions.

 

The old San Francisco Mission has a small chapel, museum, cemetery, and tiny gift shop; the basilica next door hosts regular Catholic church services. As a city, state, and national historical landmark, it is also a popular destination for tour buses.

 

Original adobe walls, inside the Mission Dolores

Original adobe walls, inside the Mission Dolores

History of Mission Dolores here.

 

Mission Dolores, 1856. Courtesy Wikipedia.

 

 

 

 

The chapel is popular and interesting, decorated and devoted. But it is busy with tourists and sounds echo.

 

Chapel interior. Courtesy Wikipedia

The cemetery, however, is hushed–with old rose bushes, palm trees, birds, and vibrant sunshine. This is where I like to be.

 

There are only two cemeteries in San Francisco, this tiny plot is one of them. It was originally much bigger.

 

Mission Dolores Cemetery

Mission Dolores Cemetery

Today the earthquake-rippled sidewalks still lead you down a path of centuries-old gravestones. It holds the markers of San Francisco’s pioneers, leaders, old residents. There is also a revered sculpture of Father Junipero Serra.

 

I like to linger here among the broken graves with worn-off names, quietly listening to the sound of the chickadee singing overhead, feeling the penetrating warmth of the sun.

 

Mission Dolores Cemetery

Mission Dolores Cemetery

Sometimes I think about the people who shaped this city, sometimes I think about Alfred Hitchcock who filmed a scene from “Vertigo” right here, and sometimes I wonder how long it will be before my parking time runs out.

 

Photo credit: Jet Eliot unless otherwise specified

 

Golden Gate GraveyardYou can read more about Mission Dolores in my newly released mystery novel. Purchase here or at Amazon or any other major book retailer.

 

 

Remembering Pearl Harbor Day

USS Arizona Memorial, Pearl Harbor

USS Arizona Memorial, Pearl Harbor

It was 75 years ago today when the attack on Pearl Harbor occurred, launching the United States into World War II.

 

I visited this Hawaiian harbor last month.  Headquarters of the U.S. Pacific Fleet and still a U.S. naval station, it was fortunately much quieter than “the day that will live in infamy.”

 

USS Arizona, Oahu

USS Arizona, Oahu

On December 7, 1941, the United States was hit by an extensive Japanese surprise aerial attack on Oahu, Hawaii. An initial wave of 183 Japanese aircraft, launched from six aircraft carriers, attacked the U.S. naval base.  A half hour later a second wave of 167 aircraft stormed in.

 

Within 90 minutes 2,403 Americans were killed, 1,178 were wounded.

 

Here the USS Arizona battleship was bombed and sunk.  It violently exploded, tearing the ship in half, instantly entombing 1,177 military people on board.

1930’s, USS Arizona. Courtesy US Navy, Wikipedia.

 

USS Arizona, sinking, on Dec. 7, 1941. Courtesy Wikipedia.

 

 

 

 

 

Today you can take a navy boat shuttle across the peaceful harbor waters to the site of the memorial.

 

Inside the USS Arizona

Inside the USS Arizona

Built in 1962 and designed by Alfred Preis, the 184-foot-long (56 m) memorial straddles the battleship’s sunken hull. Visitors arriving by boat cross a walkway bridge and enter a large, open-air room.

 

Here you experience the whipping Pacific winds and see through an opening in the floor to the sunken battleship below where over 1,100 people lost their lives.

Diagram of the sunken USS Arizona and white (vertical, center) memorial

Diagram of the sunken USS Arizona and white (vertical, center) memorial

USS Arizona beneath the Memorial. Photo: J. Pastoric, USN. Courtesy Wikipeida.

 

 

 

 

 

In the next room is a sobering shrine, a marble wall inscribed with the names of the Arizona’s honored dead. “The Tree of Life” resides here too, it symbolizes rebirth and renewal.

 

On shore is a modern visitor center with many exhibits and displays.

 

Base of the gun turret on USS Arizona

Base of the gun turret on USS Arizona

Read more about the memorial here, and U.S. Park and visitor center here.

 

I found this moving memorial another striking reminder of the beauty of peace.

 

pearl-harbor-75-aniversary
Photo credit: Athena Alexander (unless otherwise specified)

 

 

 

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China Camp

China Camp State Park, California.

China Camp State Park, California.

Named for the fishing villages that Cantonese families established here in the 1800s, China Camp is now a California State Park and a Historical Landmark.

 

Once a prime spot for harvesting shrimp, Chinese families lived busy lives here, and before that the Miwok Indians.

 

While there was much success and enterprise in the Chinese villages here in the late 1800s, harsh anti-Chinese laws put a strain on their life in the early 1900s, forcing most villagers to disperse.

 

Sampan, old Chinese shrimp-fishing boat

Sampan, old Chinese shrimp-fishing boat

The new century brought many more changes including polluted waters, loss of shrimp, and real estate development threats.

 

By the 1970s, Gulf Oil had big plans to build high-rise condominiums and commercial establishments.

 

But the residents of the surrounding area, San Rafael, California, with conservation groups and concerned citizens, protested. As a result, the land was sold to the state of California and a park was made.

 

In the early 21st century, when California had budget crises, there was more talk of closing the park. It was running on a deficit. But this too was resolved by the heroics of residents and community organizations, who formed nonprofits and raised funds, and saved the park.

 

china-camp-sign

Chinese characters: Wa Jen Ha Lio, the fishing village’s name

China Camp history and info here.

 

The park is 1,514 acres (613 ha) on a section of the San Francisco Bay. Little kids frolic on the shoreline, people jog and walk their dogs under the oak trees, picnic on the grass.

 

There is also hiking, biking, camping, kayaking, paddle boarding and other recreational activities. Gorgeous vistas across the bay, and a healthy list of birds, too.

 

Concession Stand (still open on weekends)

Concession Stand (still open on weekends)

The village buildings have been preserved, open to the public for viewing and educational touring.

 

Gentle volunteers run the gift shop selling t-shirts, and there’s an old-fashioned concession stand with a photo inside of John Wayne who filmed a movie here with Lauren Bacall (Blood Alley).

 

The beauty that is humans reaching out, making plans, and achieving their goals is here. There have been ups and downs for centuries here, subjugation and conflict, and I suppose there will be more too.

 

China Camp overview

China Camp overview

But for today, we breathe in the briny air and soak up the California sun.

 

Photo credit: Athena Alexander

 

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