Jialin Du

Three-dimensional digital modeling at actual scales is essential for digitally preserving cultural relics. While 3D reconstruction using a monocular camera offers a cost-effective solution, the lack of scale information in the resulting models limits their suitability for geometric measurements. Objects with monotonous textures, such as batteries, pose additional challenges due to insufficient feature points, increasing positional uncertainty. This article proposes a method incorporating point and line features to address the scale ambiguity in multi-view 3D reconstruction using monocular cameras. By pre-measuring the lengths of multiple sets of real line segments, building a lookup table, and associating the line features in different images, the table was input into the improved reconstruction algorithm to further optimize the scale information. Experimental results on real datasets showed that the proposed method outperformed the COLMAP method by 70.82% in reconstruction accuracy, with a scale recovery reaching millimeter-level accuracy. This method is highly generalizable, cost-effective, and supports lightweight computation, making it suitable for real-time operation on a CPU.

In multi-plane phase retrieval imaging, the accuracy and efficiency of phase retrieval algorithm are usually mutually restrictive. Specifically, deterministic algorithms struggle to achieve sufficient accuracy, while iterative algorithms consume excessive time, thereby limiting their practical application. To address this issue, we propose a deterministic-iterative integrated phase retrieval algorithm, that is, an approximate phase, which could be quickly obtained by the deterministic algorithm, is imported as an initial value into the iterative algorithm to retrieve more accurate result efficiently. To demonstrate the effectiveness of this algorithm, we simulate its performance under various iterations and diffraction distances. Additionally, experiments are conducted using a pure-phase USAF1951 target and fixed mouse fibroblasts to verify its feasibility, high accuracy, and rapid iterative convergence speed. Integrating the deterministic and iterative algorithms, this method offers a novel approach for enhancing phase retrieval.

In this paper, the incident beam called high-dimensional circular hollow sinh-Gaussian (HD-CHsG) beam with a novel wavefront is proposed, which is determined by three parameters ( m , σ ₀ , σ ₁ ). Based on the Richards-wolf vector diffraction theory, it can be focused into a longitudinal polarized optical needle through a high numerical aperture lens. The effects of the three parameters ( m , σ ₀ , σ ₁ ) on the resolution and depth of focus of the longitudinally polarized optical needle are simulated and analyzed. In the condition of ( m , σ ₀ , σ ₁ ) = (8, 0.6, 0.125), a super-diffraction longitudinal optical needle with ultra-long focal depth (resolution 0.40 λ , focal depth 18.36 λ , depth-to-width ratio 45.9:1) is generated. In addition, compared with a radially polarized incident beam whose amplitude distribution is Gaussian and circular hollow sinh-Gaussian (CHsG) distribution, the resolution and depth of focus of the longitudinally polarized optical needle obtained by focusing the HD-CHsG beam are higher. Both simulations and experiments are carried out to demonstrate the availability of our method. Our findings are of great significance to the production, manipulation, and application of longitudinally polarized optical needle.

Defocus detection technology is the key technology in the fields of laser direct writing, optical disc storage, and high-precision lithography, which directly affects the accuracy of line drawing. In this paper, using the principle of astigmatic method, combined with differential technology, a nano-level defocus detection method based on differential astigmatism for the high numerical aperture systems is proposed. Firstly, by establishing a mathematical model, the theoretical analysis and simulation of the defocus detection method based on differential astigmatism are carried out. In addition, the system parameters at the maximum sensitivity of the high numerical aperture defocus detection system is also solved. Secondly, the defocus detection experimental system based on astigmatic method was built for experimental demonstration. Finally, using the objective lens with a numerical aperture of 0.8, the focus error signal curve with a good linear relationship is obtained in this paper. The linear range is 6μm; the system sensitivity can reach 5 nm; the system detection accuracy is 30 nm, and the repeat positioning accuracy can reach 30 nm. The defocus detection method based on the high numerical aperture objective lens has the advantages of large detection range, high detection accuracy and compact system structure, which can be widely used in various new high-precision laser processing fields.