A welding helmet includes a helmet shell and a lens device mounted on the helmet shell. The lens device includes a filter control module and a single LCD panel. The logic control module controls the transmittance of the single LCD panel based on a sensed light signal and a shading-level signal designated by a user. Therefore, when the welding helmet is operated in an environment having intense light such as a welding arc, the single LCD panel will turn dark and lower its transmittance to block the intense light.
