Generating light within certain colour ranges, e.g. for runway taxiing lights - has white light source with main filter and additional compensating filter, with interference stage following absorption stage

摘要

A white light source is used, the light being filtered and reflected in the required directions. The light passes through at least one main filter and then a correction filter to compensate for any deficiencies caused by the main filter. The filtering used is not just absorption filtering but also interference filtering, though only for distinct colour ranges. The interference stage follows the absorption stage. The interference filter can be a layer on the surface of the glass absorption filter or can be a separate filter glued to the absorption filter. ADVANTAGE - Fundamentally improved light output from ground level.