Phase-shifting fringe projection methods have been developed for three-dimensional scanning (Zuo et al., 2018). However, the 3-Dimensional (3D) scanning of objects with a high dynamic reflectivity range based on structured light is a challenging task to achieve (Feng et al., 2018). The incorrect intensities captured will cause phase and measurement errors. Thus, this paper proposes a method that improves the current High Dynamic Range (HDR) (Jiang et al., 2016)) method to increase the dynamic range. The camera and projector have 3 channels, red, green, and blue, which can absorb and project these lights independently. This paper proposes a method that makes use of this by controlling the intensity of each projected for the camera. Each image can be split into 3 channels and provide 3 images which contain different intensities, then it will be used to compute the 3D information. In general, this is done by controlling the projection of red, green and blue (RGB) channel and apply the Jiang’s algorithm (Jiang et al., 2016). The results are compared and analysed with current HDR (Jiang’s method) and the regular three-step phase-shifting methods. From the experimental results, it has shown that our proposed method outperforms the current HDR and the regular three-step phase-shifting methods. Specifically, the proposed method manages to increase the dynamic range of the reflective property of objects. Additionally, our proposed method has also significantly reduced the times of 3D object measurements.

Various method was developed for the acquisition of the three-dimensional surface of an object. One of the more popular methods used is the structured light profilometry method. It can capture a high-resolution three-dimensional object in real-time. Not only that, but this method is also non-invasive, which is very suitable for the measurement of fragile samples. This paper discusses the accuracy and stability of a structured light profilometry method that is used to obtain a 3D measurement. The experiment is done by using a calibrated camera and projector. A light pattern is then projected onto the sample and captured by the camera. The accuracy of the system is investigated by capturing a flat plate with an increment of 50 µm from 0 µm to 1000 µm. The result has shown a maximum percentage error of this system is 15.76% which is 9.3511 µm, and the minimum percentage error is 0.15% which is 0.7339 µm. For the stability test, the plate was captured thirty times at the same location, and the data obtained shows the consistency of the system has a minimum and maximum standard deviation of 2.4991 µm and 6.8886 µm, which is within 7 µm. The test on the feeler gauge shows a maximum percentage error of 2.12% which is 2.1671 µm.

The relative pose between the projector and screen in a phase-measuring deflectometry (PMD) setup can result in perspective distortion and intensity errors in the projected fringe patterns. These problems degrade the sinusoidal characteristics of the fringe patterns, thus increasing phase, slope, and height errors in the PMD measurement. To overcome these issues, inverse perspective distortion and intensity modification algorithms were developed and applied to computer-generated fringe patterns before projection. The inverse perspective distortion matrices were obtained using a single image of the projected grid distortion target. The pixel intensities in the generated fringe patterns were modified using the relationship between the generated and captured pixel intensity values in grayscale images of uniform intensity. Experiments were conducted to measure the surface topographies of spherical concave and convex mirrors using a monoscopic PMD setup. Based on the experimental results, the rootmean-squared (RMS) intensity and phase errors in the projected sinusoidal fringe patterns were reduced by about 90% after using the modified fringe patterns compared to the original fringe patterns. When comparing the measured and the theoretical heightmaps, the results in PMD measurement showed an 8% and a 14% reduction of the RMS height errors in concave and convex heightmaps, respectively. The effectiveness of the algorithms in improving the accuracy of projector-based PMD measurement was demonstrated successfully.

No abstract