Exact interpretation of moiré fringe patterns in digital images

Geometric moiré enjoys the advantages of simplicity of technique and equipment, and the ability to use white light. However, resolution has been hampered by difficulties in employing more than 40 ℓ per mm. The present paper illustrates the aspects of a digital imaging system relevant to the determination of fractional fringes, and enables reliable analysis from extremely few fringes.In applying digital imaging to moiré analysis it is imperative that not only the optical characterization but also the features of the image recording system be well understood. Digitization, spatial-averaging operation and the aperture modulation are the most significant features critical to the interpretation of the digital image recorded.This paper seeks to illustrate the interaction of the moiré technique with the characteristics of a specific image recording system. Examples are presented which experimentally define the nature of moiré fringes recorded with a relatively standard digital imaging system. Further examples are presented which illustrate the influences of the features of this imaging system on the interpretation of the moiré pattern.

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