板硝子研磨面の凹凸とシュリーレン法による観測

抄録

In appraising the quality of polished plate glass surface, fine roughness down to 200300 Å is called to account, and it can be actually detected by the unaided eye. This is because of the schlieren phenomenon which takes place when the human eye looks at the concerned glass surface. A general wave-optical theory on the schlieren method is developed, taking the resolving power of the viewing system into consideration, and the contrast caused by regular and irregular roughness of the glass surface is estimated. The results shows that the optical instrument such as human eye could easily detect very fine roughness with enough contrast regardless of its resolving power, and that, for inspection of polished plate glass surface, the distance between the surface of the sample and the light-screening plate in the schlieren apparatus has to be near the range of clear vision of the eye. The schlieren patterns of various polished glass surfaces photographed by such an apparatus are compared with the multiple-beam interferograms of the same samples. Requirement for the degree of smoothness of polished glass surface appears to be more exacting than expected from the Rayleigh's λ/4 criterion.