スリット開口のFraunhofer回折による旋削面粗さ測定

抄録

A new, simple turning-surface roughness measuring method by Fraunhofer diffraction of a slit aperture is investigated. The zeroth order Fraunhofer diffraction light intensity of a slit aperture formed between a test object and a reference knife edge varies as the square of the slit half width a. The square-root value of the detected light intensity signal is proportional to the slit half width change caused by the test object surface roughness. The measurement method does not require the higher order diffraction patterns. The nonlinearity of measurement results caused by the Gaussian laser beam is discussed by a numerical analysis, and is negligible under the experimental condition of a beam radius w > 6a and a relative observation aperture h_a < 0.2. Measurements are carried out several turning-surfaces. The typical turning-surface roughness by employing our method are compared with the experimental results using a Talysurf-4, and the results of two experimental methods almost agree. The turning-surface roughness (R_max = 0.8-13 μm) is measured by employing our method.