球面の曲率牛径の測定

Abstract

A micro-interferometer of Linnik type with spherical reference mirror of the radius of 0.2 mm was designed in our laboratory for inspecting the form of the spherical tip of diamond indentors used in Rockwell hardness testing (Fig. 2). The optical system of the micro-interferometer is illustrated in Fig. 4. For the spherical mirror an accurately finished steel ball was adopted, and fine setting of the center of the steel ball on the optical axis of the objective was done by applying the method of microscopic collimation reported by the author in the previous report.Fig. 8 shows some examples of the interferograms taken by the micro-interferometer the frings of which not only cover the whole spherical part of the diamond tip but also indicate the form error in detail while the interferogram taken by the ordinary microinterferometer with plane reference mirror covers only one third of the range necessary for the prescribed form of the indentors.The convex and concave parts on the surface of the indentors compared with the spherical mirror with radius of 0.2 mm can be detected by observing the change of the fringes as the cone is displaced slightly along the optical axis of the objective. An example of the deviation of the cross-section of the diamond tip from the accurate sphere of 0.2 mm in radius is illustrated in Fig. 9.