Micro-Electro-Mechanical System (MEMS) scanning is increasingly popular in 3D surface measurement with the merits of the compact structure and high frame-rate. In this paper, we achieve real-time fringe structured 3D reconstruction by using a uniaxial MEMS-based projector. To overcome the limitations on uniaxial MEMS-based projector of lensless structure and unidirectional fringe projection, a novel isophase plane model is proposed, in which the laser line from MEMS-based projector is regarded as an isophase plane. Our model directly establishes the mapping relationship between phase and spatial 3D coordinates through the intersection point of camera back-projection light ray and isophase plane. Furthermore, a flexible calibration strategy to obtain 3D mapping coefficients is introduced with a specially designed planar target. Experiments demonstrated that our method can achieve high-accuracy and real-time 3D reconstruction.

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This Letter presents a ray phase mapping model (RPM) for fringe projection profilometry (FPP) that avoids calibrating intrinsic parameters. The novelty of the RPM, to the best of our knowledge, is the ability to characterize the imaging system with independent rays for each pixel, and to associate the rays with the projected phase in the illumination field for efficient 3D mapping, which avoids complex imaging-specific modeling about lens layout and distortion. Two loss functions are constructed to flexibly optimize camera ray parameters and mapping coefficients, respectively. As a universal approach, it has the potential to calibrate different types of FPP systems with high accuracy. Experiments on wide-angle lens FPP, telecentric lens FPP, and micro-electromechanical system (MEMS)-based FPP are carried out to verify the feasibility of the proposed method.

A phase unwrapping algorithm assisted by light field without additional time coding is proposed, which can be used in various aspects of optical imaging and metrology. The phase consistency between the light field and the industrial camera is the sticking point to convert the angular resolution of the light field into the order of phase. By virtue of the angle information recorded by the light field, the correct order can be uniquely determined from several candidate orders without confusion in the measurement volume. The mandatory requirements for system fixation and pre-calibration and the connection between the light field and industrial camera are prerequisites for order uniqueness. The mapping relationship established by the phase implies coordinate conversion, lens distortion and other factors, thus providing a high degree of stability for the transmission of phase order information. The achieved results demonstrate that our method is robust and can be taken as an effective tool for means of phase unwrapping.

2D raw image of light field (LF) camera needs to be decoded into 4D LF data for representation and processing. In decoding, the main lens is usually modeled as a thin lens while the micro-lens array is modeled as a pinhole array. Although this model takes into account the main lens distortion, it is still difficult to accurately characterize the complex imaging relationship of the LF camera. In order to obtain more accurate 4D LF data, this paper proposes a LF camera decoding method based on a two-plane ray model. By calibrating the ray corresponding to the pixel point of the LF camera, the mapping relationship between the real object point and the image point is established to obtain a new twoplane model of LF; then by interpolating and resampling on this two-plane, the correction of 4D LF data is achieved. Compared with traditional methods, our method improves the decoding accuracy of LF camera, and provides new ideas and methods for studying LF imaging.