Fringe projection profilometry (FPP) is a popular optical 3-dimensional (3D) scanning method. However, existing FPP methods often suffer from the ambiguity problem that only the wrapped phase information can be measured while the true phase information is required for 3D measurement. Although various phase unwrapping methods were suggested to recover the wrapped phase in FPP methods, most of them will fail when the target objects have complex structures. To solve this problem, we propose in this paper to embed the fringe pattern with a set of textural patterns to encode the period order of the true phase information. During the offline phase, a convolutional neural network (CNN) is trained to learn a set of filters that will be activated when they see the code patterns. When the encoded fringe image is captured, the modified morphological component analysis is first performed to extract the code pattern. It is then decoded by the trained CNN to estimate the K-map, which contains the period order of the true phase information. Experimental results show that the proposed method can measure the 3D profile of objects with abrupt jumps in height profile, where the conventional approaches often fail to perform. It also has a much higher computational efficiency due to the effective utilization of GPU by CNN.

In daily photography, it is common to capture images in the reflection of an unwanted scene. This circumstance arises frequently when imaging through a semi-reflecting material such as glass. The unwanted reflection will affect the visibility of the background image and introduce ambiguity that perturbs the subsequent analysis on the image. It is a very challenging task to remove the reflection of an image since the problem is severely ill-posed. In this paper, we propose a novel algorithm to solve the reflection removal problem based on light field (LF) imaging. For the proposed algorithm, we first show that the strong gradient points of an LF epipolar plane image (EPI) are preserved after adding to the EPI of another LF image. We can then make use of these strong gradient points to give a rough estimation of the background and reflection. Rather than assuming that the background and reflection have absolutely different disparity ranges, we propose a sandwich layer model to allow them to have common disparities, which is more realistic in practical situations. Then, the background image is refined by recovering the components in the shared disparity range using an iterative enhancement process. Our experimental results show that the proposed algorithm achieves superior performance over traditional approaches both qualitatively and quantitatively. These results verify the robustness of the proposed algorithm when working with images captured from real-life scenes.

In a fringe projection profilometry (FPP) process, the captured fringe images can be modeled as the superimposition of the projected fringe patterns on the texture of the objects. Extracting the fringe patterns from the captured fringe images is an essential procedure in FPP; but traditional single-shot FPP methods often fail to perform if the objects have a highly textured surface. In this paper, a new single-shot FPP algorithm which allows the object texture and fringe pattern to be estimated simultaneously is proposed. The heart of the proposed algorithm is an enhanced morphological component analysis (MCA) tailored for FPP problems. Conventional MCA methods which use a uniform threshold in an iterative optimization process are inefficient to separate fringe-like patterns from image texture. We extend the conventional MCA by taking advantage of the low-rank structure of the fringe's sparse representation to enable an adaptive thresholding process. It ends up with a robust single-shot FPP algorithm that can extract the fringe pattern even if the object has a highly textured surface. The proposed approach has a side benefit that the object texture can be simultaneously obtained in the fringe pattern estimation process, which is useful in many FPP applications. Experimental results have demonstrated the improved performance of the proposed algorithm over the conventional single-shot FPP approaches.

In this paper, a robust fringe projection profilometry (FPP) algorithm using the sparse dictionary learning and sparse coding techniques is proposed. When reconstructing the 3D model of objects, traditional FPP systems often fail to perform if the captured fringe images have a complex scene, such as having multiple and occluded objects. It introduces great difficulty to the phase unwrapping process of an FPP system that can result in serious distortion in the final reconstructed 3D model. For the proposed algorithm, it encodes the period order information, which is essential to phase unwrapping, into some texture patterns and embeds them to the projected fringe patterns. When the encoded fringe image is captured, a modified morphological component analysis and a sparse classification procedure are performed to decode and identify the embedded period order information. It is then used to assist the phase unwrapping process to deal with the different artifacts in the fringe images. Experimental results show that the proposed algorithm can significantly improve the robustness of an FPP system. It performs equally well no matter the fringe images have a simple or complex scene, or are affected due to the ambient lighting of the working environment.

Conventional fringe projection profilometry methods often have difficulty in reconstructing the 3D model of objects when the fringe images have the so-called highlight regions due to strong illumination from nearby light sources. Within a highlight region, the fringe pattern is often overwhelmed by the strong reflected light. Thus, the 3D information of the object, which is originally embedded in the fringe pattern, can no longer be retrieved. In this paper, a novel inpainting algorithm is proposed to restore the fringe images in the presence of highlights. The proposed method first detects the highlight regions based on a Gaussian mixture model. Then, a geometric sketch of the missing fringes is made and used as the initial guess of an iterative regularization procedure for regenerating the missing fringes. The simulation and experimental results show that the proposed algorithm can accurately reconstruct the 3D model of objects even when their fringe images have large highlight regions. It significantly outperforms the traditional approaches in both quantitative and qualitative evaluations.

This paper presents a novel marker encoded fringe projection profilometry (FPP) scheme for efficient 3-dimensional (3D) model reconstruction. Traditional FPP schemes often have large error when reconstructing 3D model of objects with abruptly changing height profile. In the proposed scheme, markers are encoded in the projected fringe pattern to resolve the ambiguities in the fringe images due to that problem. Using the analytic complex wavelet, the marker cue information can be extracted from the fringe image, and is used to restore the order of the fringes. A series of simulations and experiments have been carried out to verify the proposed scheme. Experimental results show that the proposed method can accurately reconstruct the 3D model of objects with abruptly changing height profile. It is superior to the traditional FPP methods and facilitates real time 3D measurement for color object using only a single fringe image.