Years ago, the topic of roller wave measurement in architectural glass aroused little interest among glass makers and fabricators. Windows were small enough to make distortion in reflected images hardly noticeable under most conditions. More recently, as larger glass becomes common, fabricators have been relying on so-called Zebra boards to detect major flatness defects. These days, glass with minimal roller wave distortion is now a sign of premium product quality to most building professionals. Many glassmakers still use Zebra boards, which rely on a totally subjective evaluation of the degree of distortion. The result is glass slipping through that is not only out of specification but inconsistent from batch to batch. This paper looks at various inexpensive methods,developed by Strainoptic, for accurately measuring roller wave in flat glass.
