Prismatic light transmitting panel

Claim 1

IN ALUMINAIRE COMPRISING A LIGHT SOURCE MOUNTED WITHIN FIXTURE HAVING AN OPENING THROUGH WHICH LIGHT IS NORMALLY DIRECTED INTO AN AREA TO BE ILLUMINATED, AN IMPROVED LIGHT TRANSMITTING PANEL COVERING THE OPENING, SAID PANEL HAVING (1) LIGHT REFRACTING PRISMS FORMED ON AT LEAST ONE SURFACE OF THE PANEL, AND (2) A SMALL NUMBER OF LIGHT DIFFUSING PARTICLES DISPERSED THROUGHOUT THE PANEL, (A) SAID PARTICLES BEING IN A CONCENTRATION OF 150-1,000 CRYSTALLITES PER CUBIC MM. OF MATERIAL (B) SAID PARTICLES HAVING A SIZE NOT IN EXCESS OF 0.25 MM., AND (C) THE DISTRIBUTION OF THOSE PARTICLES WHICH ARE BETWEEN 0.01 AND 0.25 MM. IN SIZE FALLING WITHIN A ZONE DEFINED BY CURVES 60 AND 62 IN FIG. 6, WHEREBY SUBSTANTIALLY ALL OF THE LIGHT TRANSMITTED THROUGH THE PANEL IS EFFECTIVELY CONCENTRATED BY THE REFRACTING PRISMS INTO A PREDETERMINED ZONE BOUNDED BY A NARROW PERIPHERAL BAND OF GRADIENT BRIGHTNESS, WHILE REFLECTED, STRAY, HIGH ANGLE LIGHT IS RENDERED RELATIVELY DIFFUSE IN PROPORTION TO ITS LONGER PATH OF TRAVEL WITHIN THE PANEL.