Abstract
We propose a new concept of single-shot deflectometry for real-time measurement of three-dimensional surface profile using a single composite pattern. To retrieve an accurate phase from one-frame composite pattern, we adapt the Fourier Transform (FT) method and the spatial carrier-frequency phase-shifting (SCPS) technique to our proposed deflectometry. Based on Lissajous figure and ellipse fitting method, we also correct the phase extraction error in SCPS technique by reducing the effect of background and modulation variations. The proposed technique is verified by comparing our measurement results with phase-shifting deflectometry, and the maximum difference between two measurement results is less than 30 nm rms. We also test the robustness to vibration and the measurement capability for dynamic object.
Highlights
Three-dimensional (3D) shape measurements of freeform surfaces using non-contact optical methods have become attractive solutions for the effective quality control of products to a variety of industrial applications such as car body panels, smartphone cover glass, and smart glasses
We introduce a new concept of single-shot deflectometry which avoids all of the disadvantages mentioned above and gives as equivalent or superior performance as phase-shifting algorithm
The main contribution of this paper locates at the step 2 and 3, where we proposed to apply spatial-carrier phase-shifting (SCPS) method for the phase retrieval of two fringe patterns after the decomposition of a composite pattern
Summary
Three-dimensional (3D) shape measurements of freeform surfaces using non-contact optical methods have become attractive solutions for the effective quality control of products to a variety of industrial applications such as car body panels, smartphone cover glass, and smart glasses. Deflectometric method utilizes phase-shifting technique[3,4,5] (PS) for reconstruction of the shape of surfaces by obtaining at least six fringe patterns (three in the horizontal and three in the vertical direction) This phase-shifting deflectometry (PSD) is quite time consuming and sometime not so suitable for industrial applications that are essential for measurements of large test samples and high speed. This method uses similar fringe pattern as previous approaches, but the main difference is color modulation and they utilize conventional three-steps phase-shifting techniques for phase retrieval instead of Fourier transform. It can avoid errors come from Fourier-based techniques. Our proposed method can provide three-dimensional surface profile measurement for dynamic object in real time
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