Abstract Directly using wrapped phases may cause a problem of phase ambiguity in fringe-projection-based three-dimensional (3D) imaging. In our previous work, the phase ambiguity was addressed by introducing light-field imaging to associate a wrapped phase-encoded field in the image space with several candidates of spatial points in the object space to identify the correct fringe orders for absolute phase unwrapping. The candidate spatial points with absolute phases can be reconstructed by satisfying the mandatory requirements of system fixation and pre-calibration, which may lack flexibility and applicability. Since we also illustrated that the correspondence cue in an unwrapped phase-encoded field could be used for accurate light-field depth estimation, an instructive question is whether or not depth cues of the light-field imaging can provide constraint conditions to deal with the phase ambiguity without these systematic requirements. To this end, a method for structured-light-field 3D imaging is proposed. The wrapped phase-encoded field was processed to be locally continuous with respect to the phases in specific angular coordinates. After that, the correspondence cue focusing on the local angular variance of the processed wrapped phase-encoded field was used to estimate depths correctly without the requirement of system pre-calibration. Furthermore, comparative experiments under different measurement conditions, including the changes of the fringe period of projected patterns, the focal length of the projector, and the relative orientation among system components, produced the consistent measurement results. Consequently, the proposed method is proved to adapt to the changes in the measurement environment and be a flexible way for structured-light-field 3D imaging without the need for phase unwrapping.

中文翻译：

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无相位展开的结构光场 3D 成像

摘要 直接使用包裹相位可能会导致基于条纹投影的三维（3D）成像中的相位模糊问题。在我们之前的工作中，通过引入光场成像将图像空间中的包裹相位编码场与物体空间中的几个候选空间点相关联，以识别绝对相位展开的正确条纹顺序，从而解决了相位模糊问题。具有绝对相位的候选空间点可以通过满足系统固定和预校准的强制性要求来重建，这可能缺乏灵活性和适用性。由于我们还说明了展开的相位编码场中的对应线索可用于准确的光场深度估计，一个有启发意义的问题是光场成像的深度线索是否可以提供约束条件来处理没有这些系统要求的相位模糊。为此，提出了一种用于结构光场 3D 成像的方法。包裹的相位编码场被处理为相对于特定角坐标中的相位是局部连续的。之后，针对处理后的包裹相位编码场的局部角方差的对应线索用于正确估计深度，而无需系统预校准。此外，在不同测量条件下的对比实验，包括投影图案的条纹周期、投影仪的焦距以及系统组件之间的相对方向的变化，产生一致的测量结果。因此，所提出的方法被证明可以适应测量环境的变化，并且是一种灵活的结构光场 3D 成像方法，无需相位展开。