Measurement of Three-Dimensional Curved Surface of Machine Part Using Holographic Interferometry. 1st Report. Correspondence between Coordinate System of Measured Surface and That of its Image.

Abstract

In interferometry measurement using laser holography, it is not easy to find a definite relation between the measured image pattern and the topography of the actual surface. The main reason is that each of the measuring object, measurig apparatus, electronic data processor and CRT display has its own coordinate system, and the transformig or mapping relation between them is obscure. In this report, measured image of some test pieces with plane and cylindrical surfaces were compared with their simulated figure. Subsequently, tooth flank of a gear, which is a three-dimensional curved suface in which high accuracy in form is required, was chosen as the object of measurement. To obtain the relation between each coordinate system of a measuring object, of optical parts in the measuring appartus and of the image on a CRT, a method is proposed which requires the simulated contour of the diffracted figure of the objective curved surface to be measured corresponding to and fitting the actually measured and observed image pattern on the CRT. The experimental and simulated results indicate that the pixel position of the image on the CRT can correspond to the coordinate value of the tooth flank, and that the transformation of the measured image on the CRT to the error surface of tooth flank defined on the plane of action of the gear, i. e., to the tooth form chart and to the tooth trace form chart, is possible.