A Fast and Accurate Phase-Based Displacement Measurement Method Based on Complex Laplacian Pyramid With Condensed Focus Frequency

The phase-based displacement measurement method has received increasing attention due to its high subpixel accuracy and robustness against illumination variations. However, its overall performance is constrained by the computational inefficiency introduced by the additional phase extraction step. Recent studies have attempted to improve computational efficiency by proposing new phase extraction techniques, but these approaches often suffer from limited robustness, leading to reduced measurement accuracy. To overcome this limitation, a novel phase extraction method is developed to preserve the high measurement accuracy of traditional phase-based methods while significantly enhancing computational efficiency. Featuring a simple mathematical structure and a condensed focus frequency at each scale level of the Laplacian pyramid, the proposed Complex Laplacian Pyramid with Condensed Focus Frequency (CLP-CFF) method achieves a better balance between accuracy and efficiency than existing phase-based methods. The accuracy, computational efficiency, and robustness of the CLP-CFF method are further validated through laboratory and real-world experiments.