Accuracy characteristics of a Fresnel method for measurement of objects dimensions in coherent light are investigated. Free space being an optical element transforms with high accuracy the input image of the object into its Fresnel image. Two main sources of a systematic measurement error are estimated analytically, including nonuniform illumination of the object and interference of the edges images (an interference effect). An effective algorithm of reducing for the first of these errors by many factors of ten is proposed. It takes into account the behavior of the illuminating field and its derivative in the vicinity of the boundaries of the object.
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