Dynamic projection theory for fringe projection profilometry

Abstract

Fringe projection profilometry (FPP) has been widely used for three-dimensional reconstruction, surface measurement, and reverse engineering. However, FPP is prone to overexposure if objects have a wide range of reflectance. In this paper, we propose a dynamic projection theory based on FPP to rapidly measure the overexposed region with an attempt to conquer this challenge. This theory modifies the projected fringe image to the next better measurement based on the feedback provided by the previously captured image intensity. Experiments demonstrated that the number of overexposed points can be drastically reduced after one or two iterations. Compared with the state-of-the-art methods, our proposed dynamic projection theory measures the overexposed region quickly and effectively and, thus, broadens the applications of FPP.

Automatic exposure control method for 3D shape measurement of specular surface based on digital fringe projection

“…In general, the existing techniques can be classified into two categories: adjusting light-intensity technique and adjusting exposure technique. The former is used to adjust the intensity of the projection patterns to obtain the unsaturated images [7][8][9][10][11][12][13][14][15]. In particular, it is used to increase the projecting intensity for low-reflective surfaces and reduce the projecting intensity for high-reflective surfaces.…”

Hybrid 3D Shape Measurement Using the MEMS Scanning Micromirror

“…Some other researchers have attempted to adjust the parameters of the camera and projector to handle the surface with large reflection variations. Lin et al [21,22] suggest adjusting the maximum input gray level of projecting image globally, while Chen et al [23,24] proposed adjusting projecting images pixel-by-pixel. In [16,25], the author proposes projecting a set of fringe images that are captured with different exposures.…”

“…In [16,25], the author proposes projecting a set of fringe images that are captured with different exposures. For [16,21,22,23,24,25], the reflection of the surface needs to be calibrated first. Then, by fusing these images captured with different parameters, a new fringe pattern with fewer saturated regions can be obtained.…”

“…Then, by fusing these images captured with different parameters, a new fringe pattern with fewer saturated regions can be obtained. Although Jiang et al [16,20,21,22,23,24,25] improve the performance without adding any extra equipment, they need to project or capture a lot of images when the measuring surface has very complex reflection variations. On the other hand, these approaches still use an FPP principle, which can be ineffective for extreme reflection areas.…”

High speed 3D photomechanics testing via additional temporal sampling

“…Then, Chen and Zhang (Chen and Zhang, 2016) discovered that saturated fringe patterns with its number of phase shifting steps N = P/2 pixels (P denotes pixels per period of fringe) in fact produces high quality 3D reconstruction for shiny surfaces. Furthermore, another special type of research was carried out which adaptively modifies the projector's intensity levels (Li and Kofman, 2014;Waddington and Kofman, 2014a,b;Lin et al, 2016Lin et al, , 2017aSheng et al, 2017) or color information (Kuo et al, 2016) based on the feedback from previously captured data. Overall, all these state-of-art HDR methods have achieved great successes when measuring high-contrast or shiny surfaces with different speeds, flexibilities and complexities.…”