colmascopes

Noun

colmascope (plural colmascopes)

1. An instrument for visualising stressed regions, especially internal regions, in substances such as glass, by detecting differences in the degree of rotation of the plane of polarisation, generally by placing the object between crossed polarizers.
   • A device like those in which one polariser is fixed and the other rotatable — often with marked gradations — is called a polariscope or a polarimeter. One in which the polarisers are fixed at right angles is often called a "colmascope", but this name is actually a trademarked device, first...
   • Why did American Optical come up with the name "Colmascope" …? Certainly they wanted a name that would set their device apart from the other polariscopes on the market, so they cast about for something without "polari-" in the name. Their choice seems to derive from Greek root kolmo- meaning...Stephen R. Wilk (2021), Sandbows and Black Lights, pages 47–