A computer-generated diffractive optical element to produce 4×4 spot matrix images was fabricated by electron-beam lithography. The element was applied to the inspection of paper sheets. Images of spot matrices were analyzed, and agreementbetween the reflectance measured by the present sensor and a spectrophotometer was observed. The sensor image was able to yield information about local curvature as well as defects. Moreover, sensor images from surfaces of different paper samples revealed material surface anisotropy in the cross-correlation analysis of image data.
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