Low visibility simulation screen

Claim 1

A LOW VISIBILITY SIMULATION SCREEN FOR USE BY AN INSTRUCTOR IN TRAINING A PILOT TO LAND AN AIRCRACT IN CONDITIONS OF LOW VISIBILITY SAID SCREEN BEING DISPOSED IN THE FIELD OF VISION OF EACH TRAINEE BUT NOT IN THE FIELD OF VISION OF HIS INSTRUCTOR, SAID SCREEN COMPRISING IN A FIRST PLANE A PLURALITY OF PARALLEL NARROW OPAQUE ZONES SPACED APART BY ZONES OF AT LEAST PARTIAL TRANSPARENCY, AND IN A SECOND PARALLEL AND ADJACENT PLANE A SECOND PLURALITY OF NARROW OPAQUE ZONES PARALLEL TO THE FIRSTMENTIONED NARROW OPAQUE ZONES AND SPACED APART BY ZONES OF AT LEAST PARTIAL TRANSPARENCY, THE OPAQUE ZONES IN SAID FIRST AND SECOND PLANES BEING UNIFORM IN WIDTH AND SPACING AND HAVING A WIDTH GREATER THAN THAT OF THE SPACING, THE EDGES OF THE OPAQUE ZONES BEING VIGNETTED TO PROVIDE GRADUAL TRANSITION FROM OPACITY OF TRANSPARENCY AND VICE VERSA, THE SPACES BETWEEN OPAQUE ZONES IN SAID FIRST AND SECOND PLANES BEING SO SMALL THAT A TRAINEE IS NOT CONSICOUS OF THE EXISTENCE OF SEPARATE OPAQUE AND TRANSPARENT ZONES BUT RATHER OF A DIFFUSED VIEW OF THE EXTERNAL SCENE.