At the top, the original nine-foot tall Fresnel lens
, made in France, still serves as beacon, but now is lit by a 1,000-watt bulb, whereas in the old days those tending the lighthouse had to haul oil up in buckets to keep the lens alight.
Now, as the first step in what is eventually intended to be a full-scale refurbishment of the lighthouse, the Village of Sleepy Hollow and the Westchester County Department of Parks have commissioned and installed an exacting replica of the original fourth-order Fresnel Lens
and rotating light that once operated atop the lighthouse.
Other interesting artifacts that will be on exhibit include the fourth-order Fresnel lens
from the Ship Island lighthouse.
The concentrator is a Fresnel lens
, a prism-like optics design that was originally developed to increase the intensity of beams emanating from lighthouses.
But for all of the detailed historical description that populates her careful depiction of the Fresnel lens
and its production in the 19th century, the book lacks a compelling narrative or even larger context within which this feat can be fully appreciated.
Mr Scott added: "We also had a series of accidents where cars were undertaking us in the blind spot of our trucks - we have installed the Fresnel lens
, which stick on the window and can show you the blind spot as you look across.
Though most people do not know its name, the Fresnel lens
is a familiar object, a floppy or solid lens engraved with concentric circles that focus and intensifies light far more than is possible with a metal mirror, and without the great weight of a traditional lens.
The design of the Fresnel lens
allows for the construction of a lens with a large aperture and short focal length, without the mass and volume of material that would be required by a lens of conventional design.
The light was automated in 1983 when the Fresnel lens
held within its steel cage and floating on a bath of mercury, turned by a clockwork system was replaced with the modern "car headlight" lamps.
Featuring a "highly efficient light source" with a Fresnel lens
, the Nova 270's light output is approximately equivalent to 2,000W of tungsten Fresnel.
In addition, the pilot stated that his carrier landing technique was to use his Automated Carrier Landing System (ACLS) needles as his primary reference and use the Fresnel Lens
Optical Landing System, or meatball, as a backup for glide slope information.
Through partnering with eSolar, Ferrostaal now adds solar power tower technology to its current concentrating solar thermal portfolio, which includes parabolic trough and Fresnel lens