Improved Fourier transform profilometry for the automatic measurement of 3D object shapes

Pixel-by-pixel absolute three-dimensional shape measurement with modified Fourier transform profilometry

“…The FTP method works well if the surface geometry changes slowly and surface texture is not very rich. To improve the performance of the FTP method, Guo et al [6] proposed a modified FTP method that uses two π-shifted fringe patterns:…”

“…However, it is challenging to achieve high measurement quality with a single pattern due to the impact of the DC component (e.g., ambient lighting, surface texture). Guo et al [6] developed a modified FTP method to improve measurement quality by adding one more phase-shifted fringe pattern with the same period that it reduced the impact of the DC component.…”

“…This paper presents a novel method that requires only two fringe patterns for pixel-by-pixel absolute phase recovery. The proposed method is similar to the modified FTP method proposed by Guo et al [6] in that we also use two fringe patterns to reduce the impact of the DC component and apply the Fourier transform method to retrieve the phase. However, our method differs from the method proposed by Guo et al [6] because (1) we use two different frequencies instead of the same frequency for these two fringe patterns; (2) we realize a temporal phase unwrapping for pixel-by-pixel absolute phase recovery, yet Guo et al's method recovers only the relative phase since the spatial phase-unwrapping method is adopted; and (3) our method could have a lower phase quality because a lowfrequency component can affect the effective bandwidth of the high-frequency component.…”

“…The proposed method is similar to the modified FTP method proposed by Guo et al [6] in that we also use two fringe patterns to reduce the impact of the DC component and apply the Fourier transform method to retrieve the phase. However, our method differs from the method proposed by Guo et al [6] because (1) we use two different frequencies instead of the same frequency for these two fringe patterns; (2) we realize a temporal phase unwrapping for pixel-by-pixel absolute phase recovery, yet Guo et al's method recovers only the relative phase since the spatial phase-unwrapping method is adopted; and (3) our method could have a lower phase quality because a lowfrequency component can affect the effective bandwidth of the high-frequency component. Conceptually, the proposed method works as follows: (1) we apply Fourier transform to the difference images of these two fringe patterns, (2) we use the bandpass filters to separate the low-frequency and highfrequency components, (3) we compute the wrapped phase for both frequency components, and (4) finally we unwrap the high-frequency phase pixel by pixel by referring to the low-frequency phase.…”

FTP 3D restructure using in smooth tracks

“…It develops rapidly because of the good characters of non-contact, high precision, high speed, and high degree of automation [1][2]. Yet this phase-based profilometry is suitable for measuring objects with diffuse surface.…”