Page 15 - NyghtVision Volume 5 #4

In 1823, a team led by Augustin-Jean Fresnel designed a

lens that could create a beam of light visible for 20 miles.

Funded by the French Government for use in lighthouses, the

lens was lighter and thinner than one ground from a single

piece of glass. Fresnel arranged an array of prisms to capture

the radiating light from a single source then to redirect it in

parallel beams. Fresnel’s new lens was first installed in the

Cordouan lighthouse at Gironde, France.

Master craftsmen in Paris produced most Fresnel lights

installed in US lighthouses.

There are six orders (magnitudes) of Fresnel lights deter-

mined by the light’s location: higher orders (See photos 1-2)

are major landfall lights, the middle range (See photos 3-4)

for coastal navigation, and the smallest (See photos 5-6) for

bays and estuaries. The largest light above order 1 is a hy-

per-radial light; the only US hyper-radial is located in Hawaii.

Light Houses provided unique signature light patterns spe-

cific to their location that serve mainly as navigation aids for

mariners.
1
For NyghtFalcon still imaging, Falcon has developed a light-

ing methodology using Fresnels to benefit from the consis-

tency of the light across the beam and the soft fall-off at the

edge. (see “Lighting the Unlightable” series.)

 Haceta Head Light, Florence, OR

Autumn 2015 | 15
14 | Andy Walcott