In-Process Measurements of Surface-Roghness under Dynamic Speckle Illumination

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A new method to measure the surface-roughness in process at non-contact have been investigated. The main results in this work are written as follows :1. Basic Studies to Determine Two Kinds of Roughness(1) Under the dynamic speckle illumination, the scattered field at a far field obeys Gaussian statistics. From properties of the scattered light, we deduced the intensity correlation function in the explicit form. So, the speckle size of the light has been found to depend on the surface roughness.(2) The speckle size depends on fluctuations of the integrated intensity of the scattered light. If the 2nd order moment of the integrated intensity is measured two times for different experimental conditions, longitudinal and lateral roughness can be determined.2. In-process measurements of surface-roughness(1) Use of two-lens imaging system is able to measure the roughness from 0.01mum to 0.5 mum.(2) We developed the apparatus to measure the 2nd order moment by digitally processing the video signal from TV camera at high speed. If the 8-bit A/D converter is used, the moment is measured at 2% accuracy, and the roughness can be determined 2-dimensionally.(3) We developed the another apparatus to measure the intensity ratio of the lights scattered to different direction. This apparatus can determine the surface roughness of cold rolled steels in process.