High-speed 3D surface profilometry employing trapezoidal phase-shifting method with multi-band calibration for colour surface reconstruction

Abstract

This article presents a new optical measurement method employing a HSI (Hue, Saturation and Intensity) colour model to form trapezoidal structured patterns for morphology reconstruction of a measured object at a high speed. Profilometry on objects having nonmonochromatic surfaces is considered as one of the remaining most challenges faced by the currently existing structured-light projection methods since the surface reflectivity to red, green and blue light may vary significantly. To address this, an innovative colour calibration method for hue component is developed to determine the accurate reflectivity response of the measured surface. The trapezoidal colour pattern is calibrated to compensate the hue-shifted quantity induced by the reflective characteristics of the object's surface. The developed method can reconstruct precise 3-D surface models from objects by acquiring a single-shot image, which can achieve high-speed profilometry and avoid in-situ potential measurement disturbances such as environmental vibration. To verify the feasibility of the developed methodology, some experiments were conducted to confirm that the measurement accuracy can be controlled within 2.5% of the overall measurement range and the repeatability of 3.0% within 3 can be achieved.

Robust measurement of the diffuse surface by phase shift profilometry

“…However, it is almost impossible to separate the captured RGB phase pattern into three independent phase patterns in reality. Many researchers [26][27][28][29][30][32][33][34][35], have claimed that their one-shot method is capable of measuring the shape of a dynamic and diffuse surface. Among them [32][33][34], tried to modulate the fourshifted phase patterns into one composite pattern and wished to obtain the distortion information from the demodulated patterns.…”

Single-shot three-dimensional reconstruction based on structured light line pattern

“…Based on the surface characteristics of the object, the non-contact three-dimensional surface imaging techniques could be divided into two categories: techniques to measure the specular surfaces [1][2][3][4][5] and techniques to measure the diffuse surfaces [6][7][8][9][10][11][12][13][14][15][16][17][18] . No matter for the specular surfaces or the diffuse surfaces, the robust measurement with one-shot is very challenging, however, it is highly desired especially when the measured surfaces are dynamic and deformable.…”

“…No matter for the specular surfaces or the diffuse surfaces, the robust measurement with one-shot is very challenging, however, it is highly desired especially when the measured surfaces are dynamic and deformable. As a result, many one-shot methods have been proposed for specular surface measurement [1][2][3][4][5] and diffuse surface measurement [11][12][13][14][15][16][17][18] . Each proposed method has its own merits or limitations and its application is also limited.…”

“…Consequently, phase shift profilometry has limited applications in measuring the shapes of moving objects or deformable objects. Despite the limitations, pioneering researchers had tried to measure the 3D shapes of the moving objects by utilizing the phase shift method [11][12][13][14][15] . Lau et al tried to measure the 3D shape of the moving object by projecting multiple phase patterns with time-synchronized illumination [11] .…”

“…Later, Yue et al modulated five phase patterns into one composite pattern and achieved one-shot projection of the composite pattern to measure the 3D shape of the object [14] . Chen et al also achieved one-shot reconstruction of color surface with the phaseshifting method by employing the Hue Saturation Intensity (HSI) color model [15] . Besides the phase-shifting based methods, different methods had also been exploited to measure the three-dimensional shapes of the moving objects [16][17][18][19] .…”