| 摘要 |
<p>The invention provides an electro-optic welding lens assembly (2) for use in a welder's helmet (1) or protective eyeshield. It includes at least one liquid crystal filter element (14) adapted to be controlled with regard to its light transmission as well as a control means (11, 12, 13) for changing the rate of light transmission of the liquid crystal filter element (14). The control means comprises a first manually adjustable control circuit (13) operating independently of the amount of light falling on the lens assembly (2) and including means to adjust the rate of light passing through the liquid crystal filter element (14). Further, there is provided a second automatically operated control circuit (11) operating in relation to the amount of light falling on the lens assembly (2). The second control circuit operates only within a range of light intensity above a predetermined treshold value to limit the rate of transmission of light passing through the liquid crystal filter element (14). Thereby, the second control circuit (11) overrides and compensates, respectively, the effect of the first control circuit (13) in the range above said treshold value of light intensity falling on the lens assembly (2), with the effect that the lens assembly can not be opened too much if harmful light rays are present in the ambient.</p> |
