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Lighthouse lighting at sea

Lighthouses are designed to provide visible signals to distant ships at sea. Under specified climatic conditions, their maximum visible range should be as far as possible within the limits of the curvature of the earth. The intensity of the signal light is determined by the required sight distance. If the lighthouse uses flashing, the Blondel Rey law can be used to calculate the required intensity. The signal light must be clear and easy to identify which lighthouse it is from. The color and flash characteristics of the light should be different from other lighthouses and from other nearby signal lights.

The flash signal of a lighthouse is generally controlled by a rotating light screen or light gate, and can also be controlled by a rotating optical device that can produce a narrow beam of light. Recently, extremely high-intensity flash tubes have been studied and tested. It is more economical to use flash tubes on lighthouses, but mariners seem to prefer rotating flash signal lights because of the glare effect of flash tubes.

The requirements for lighthouse lights are small size, high brightness and long life. This allows the matching optical device to produce a very high-intensity and narrow-angle beam to meet the needs of the lighthouse. At present, some places have adopted 2000-watt short-arc Xenon Lamps, but most lighthouses still use high-power incandescent lamps.

Recently, gas lasers have been developed as the light source of lighthouse signal lights. Lasers can emit narrow and extremely high-intensity monochromatic beams, and their transmittance is extremely high under poor visibility conditions. From the perspective of development prospects, there will be more advantages if lasers are combined with common lighthouse equipment.

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