Light screens, esp. for protective spectacles used in welding - where two side-shaped Moire grids are used to obtain sharp image

摘要

The screen uses the known Moire effect obtd. via the use of two line screens or strips; and the transparency function of the lines or grids is sine-shaped. The screen is pref. used for all types of appts. providing protection for eyes, esp. in protective appts. employed during welding. With conventional Moire screens, both positive and negative refraction occurs so several images are formed and observation of the weld is impaired. The invention is designed to eliminate the subsidiary images so the observer obtains a clear picture through the screen.