The Fresnel Lens - A parabolic type lens invented by French physicist Augustin Fresnel, commonly used in lighthouses throughout the world. Classified by size into six "orders" based on the lens focal length. The First Order is the largest at 12 feet tall with a diameter of 6 feet and a focal length of 36 inches. The Sixth Order is the smallest at 2 feet tall with a diameter of 1 foot and a focal length of 5.9 inches.

First Order Fresnel

Photographer: Merle Bishop

Lens on display at the Key West Lighthouse Museum in Key West, Florida.

Second Order Fresnel - White Shoal

Photographer: Keith Churill

The original lens from the White Shoal Lighthouse in the Straits of Mackinac. The lens is currently on display in the museum at Whitefish Point.

Second Order Fresnel - Spectacle Reef

Photographer: Keith Churill

The original lens from the Spectacle Reef lighthouse now on display at the Great Lakes Historical Society Museum in Vermilion, Ohio.

Fourth Order Fresnel

Photographer: Merle Bishop

Lens on display at the Key West Lighthouse Museum in Key West, Florida.