Moiré analysis for assessment of line registration quality

This paper introduces objective macro and micro line registration quality metrics based on Moiré interference patterns generated by superposing a lenticular lens grating over a hardcopy test page consisting of high-frequency Ronchi rulings. Metrics for macro and micro line registration are defined and a measurement procedure is described to enhance the robustness of the metric computation over reasonable variations in the measurement process. The method analyzes low frequency interference patterns, which can be scanned at low resolutions. Experimental measurements on several printers are presented to demonstrate a comparative quality analysis. The metrics demonstrate robustness to small changes in the lenticular lens and grating superposition angle. For superposition angles varying between 2° and 5°, the coefficients of variance for the two metrics are less than 5%, which is small enough for delineating between test patterns of different print quality.