フレネルレンズ
Table Bluff Lighthouse was built in 1892. A fixed, fourth-order Fresnel lens was removed from the Humboldt Harbor Light and installed in the tower at Table Bluff in late October 1892. In 1911, the fixed Fresnel lens was replaced with a revolving one. A modern optic was installed in the tower, and the Fresnel lens was shipped to San Diego to be displayed in the Old Point Loma Light. The lighthouse was deactivated in 1975.