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This paper presents an adaptive focus stacking method for large depth-of-field (DOF) 3D microscopic structured-light imaging systems. Conventional focus stacking methods typically capture images under a series of pre-defined focus settings without considering the attributes of the measured object. Therefore, it is inefficient since some of the focus settings might be redundant. To address this problem, we first employ the focal sweep technique to reconstruct an initial rough 3D shape of the measured objects. Then, we leverage the initial 3D data to determine effective focus settings that focus the camera on the valid areas of the measured objects. Finally, we reconstruct a high-quality 3D point cloud using fringe images obtained from these effective focus settings by focus stacking. Experimental results demonstrate the success of the proposed method.

Conjugated polymers consist of complex backbone structures and side‐chain moieties to meet various optoelectronic and processing requirements. Recent work on conjugated polymers has been devoted to studying the mechanical properties and developing new conjugated polymers with low modulus and high‐crack onset strain, while the thin film mechanical stability under long‐term external tensile strain is less investigated. Here we performed direct mechanical stress relaxation tests for both free‐standing and thin film floated on water surface on both high‐T_gand low‐T_gconjugated polymers, as well as a reference nonconjugated sample, polystyrene. We measured thin films with a range of film thickness from 38 to 179 nm to study the temperature and thickness effect on thin film relaxation, where an apparent enthalpy–entropy compensation effect for glassy polymer PS and PM6 thin films was observed. We also compared relaxation times across three different conjugated polymers and showed that both crystalline morphology and higher modulus reduce the relaxation rate besides higher glass transition temperature. Our work provides insights into the mechanical creep behavior of conjugated polymers, which will have an impact on the future design of stable functional organic electronics.

Wearable devices benefit from the use of stretchable conjugated polymers (CPs). Traditionally, the design of stretchable CPs is based on the assumption that a low elastic modulus (E) is crucial for achieving high stretchability. However, this research, which analyzes the mechanical properties of 65 CP thin films, challenges this notion. It is discovered that softness alone does not determine stretchability; rather, it is the degree of entanglement that is critical. This means that rigid CPs can also exhibit high stretchability, contradicting conventional wisdom. To inverstigate further, the mechanical behavior, electrical properties, and deformation mechanism of two model CPs: a glassy poly(3‐butylthiophene‐2,5‐diyl) (P3BT) with anEof 2.2 GPa and a viscoelastic poly(3‐octylthiophene‐2,5‐diyl) (P3OT) with anEof 86 MPa, are studied. Ex situ transmission X‐ray scattering and polarized UV–vis spectroscopy revealed that only the initial strain (i.e., <20%) exhibits different chain alignment mechanisms between two polymers, while both rigid and soft P3ATs showed similarly behavior at larger strains. By challenging the conventional design metric of lowEfor high stretchability and highlighting the importance of entanglement, it is hoped to broaden the range of CPs available for use in wearable devices.

This Letter presents a novel, to the best of our knowledge, method to calibrate multi-focus microscopic structured-light three-dimensional (3D) imaging systems with an electrically adjustable camera focal length. We first leverage the conventional method to calibrate the system with a reference focal lengthf₀. Then we calibrate the system with other discrete focal lengthsf_iby determining virtual features on a reconstructed white plane usingf₀. Finally, we fit the polynomial function model using the discrete calibration results forf_i. Experimental results demonstrate that our proposed method can calibrate the system consistently and accurately.

Measuring speed is a critical factor to reduce motion artifacts for dynamic scene capture. Phase-shifting methods have the advantage of providing high-accuracy and dense 3D point clouds, but the phase unwrapping process affects the measurement speed. This paper presents an absolute phase unwrapping method capable of using only three speckle-embedded phase-shifted patterns for high-speed three-dimensional (3D) shape measurement on a single-camera, single-projector structured light system. The proposed method obtains the wrapped phase of the object from the speckle-embedded three-step phase-shifted patterns. Next, it utilizes the Semi-Global Matching (SGM) algorithm to establish the coarse correspondence between the image of the object with the embedded speckle pattern and the pre-obtained image of a flat surface with the same embedded speckle pattern. Then, a computational framework uses the coarse correspondence information to determine the fringe order pixel by pixel. The experimental results demonstrated that the proposed method can achieve high-speed and high-quality 3D measurements of complex scenes.

This paper presents an absolute phase unwrapping method for high-speed three-dimensional (3D) shape measurement. This method uses three phase-shifted patterns and one binary random pattern on a single-camera, single-projector structured light system. We calculate the wrapped phase from phase-shifted images and determine the coarse correspondence through the digital image correlation (DIC) between the captured binary random pattern of the object and the pre-captured binary random pattern of a flat surface. We then developed a computational framework to determine fringe order number pixel by pixel using the coarse correspondence information. Since only one additional pattern is used, the proposed method can be used for high-speed 3D shape measurement. Experimental results successfully demonstrated that the proposed method can achieve high-speed and high-quality measurement of complex scenes.