| 摘要 |
PURPOSE:To obtain flatness readily, by holding a medium having a high refractive index with a medium having the refractive index lower than said medium, using an interference film device having a pair of interfaces, and judging the sequence of the change in lightneess in three stages. CONSTITUTION:A device comprises a first dielectric layer 28 having a relatively high refractive index and a second dielectric layer 30 and a third dielectric layer 32, which hold the layer 28 and have a refractive index lower than that of the layer 28. There are a first interface 34 and a second interface 36. The reflected light beams from the first interface 34 and the second interface 36 reach a half mirror 14 through a collimator lens 16 together with the reflected light beam from a material to be checked 20. The light beams are reflected by the half mirror 14 and received by an industrial TV camera 24 through a condenser lens 22. Interference fringes constituting an interference image 38 comprise the bright fringes, whose lightness is large, the intermediate fringes, whose lightness is medium, and the dark fringes, whose lightness is small. The sequence of the lightness corresponds to the slant direction of the surface of the material to be checked.
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