Yang Zhu

The double-helix point spread function (DH-PSF) inherently suffers from a trade-off between axial range and sensitivity, which limits its use in optical alignment and focal-plane tracking tasks that require both wide-range acquisition and high-precision localization. To overcome this limitation, we propose a fast axial displacement sensing method that integrates a radially segmented double-helix point spread function (RS-DHPSF) with multi-feature hierarchical demodulation. By tailoring the phase responses of the inner and outer radial zones, the RS-DHPSF simultaneously provides a wide axial capture range and high sensitivity in the central region. We further establish a non-ideal optical model incorporating phase quantization, physical noise, and residual aberrations to evaluate axial localization performance. To efficiently decode the complex RS-DHPSF patterns evolving with axial displacement, we further develop a hierarchical region-of-interest chirp z-transform normalized cross-correlation (ROI-CZT-NCC) algorithm constrained by multi-feature candidate intervals. Simulation and experimental results show that the proposed method reduces the per-frame localization time by approximately 90% while achieving a continuous axial measurement range of approximately 7 mm, with a mean absolute error (MAE) of 0.771 μm over the full range and a reduced MAE of 0.419 μm within the central ±250 μm region.

Angle measurement serves as a foundational technology in the field of precision measurement and control, playing an indispensable role in key areas such as advanced manufacturing, aerospace, precision detection and large-scale structural health monitoring. As measurement technology continues to advance, there is an increasing demand for complexity, accuracy, and long-term stability. Angle measurement technology continues to evolve to address these complex application challenges. This review systematically analyses two categories of angle measurement methods: electronic measurement methods and optoelectronic measurement methods. Following the ‘method-problem-solution’ framework, the performance characteristics of both categories are systematically analysed. Electronic methods, capitalising on their high integration and low cost, achieve large-scale application, while optoelectronic methods excel in ultra-high precision and multi-degree-of-freedom measurement. With the aim of offering intuitive technical selection guidance, this paper provides a performance classification map and dedicated parameter tables for each technology. Concurrently, addressing the aforementioned challenges, we summarise the latest solutions including structural innovations, principle improvements, and integration techniques. This is intended to furnish researchers and practitioners with clear knowledge consolidation and references for technical selection in both engineering practice and scientific research.

As the demand for stability in ultra-high precision optoelectronic system alignments continues to increase, synchronous three-dimensional spatial state measurements are necessary to ensure the accuracy and reliability of detection data. In this context, a three-dimensional interferometry system based on computer-generated hologram (CGH) wavefront modulation was proposed, in which an aspheric mirror was used as a reference mirror to reflect in real time the wavefront changes caused by platform instability. The relative position calibration of optoelectronic elements and wavefront modulation are realized based on CGH. By employing a dual-constraint ray tracing method and a spatial state sensitivity matrix, a model was established to realize a mapping relationship between the reference mirror three-dimensional spatial instability state parameters and the fitted Zernike polynomial coefficients of the wavefront difference grid matrix. The experimental validation of the proposed three-dimensional spatial state measurement system was conducted. Measurement results were obtained from wrapped phase data processed using Spatial phase unwrapping by applying Zernike polynomial fitting and the mapping relationship. The results demonstrated the system’s capability to achieve real-time synchronous measurement of tilt and displacement in three dimensions with a high level of accuracy, exhibiting a maximum deviation error of less than 0.2″ for tilt and 4μm for displacement, respectively. The system demonstrated excellent stability throughout the experiments. The relative standard uncertainties for tilt and displacement measurements are 1.74% and 2.98%, respectively.

Infrared invisibility has continued to develop in recent decades, triggered by novel physics, advanced fabrication technology and raw materials. However, the quick response of infrared stealth during transmedia (water–air/water–land) movement, which is important in practical scenarios, has not been investigated. Here, we employ the random thermal effect of the interaction between laser and matter to construct a bionic flexible thin-film superhydrophobic infrared invisibility cloak. The average emissivity of invisibility cloak is 0.224 over 8–14 ${{\mu }}\text{m}$ , and specular reflectivity at the incident angle of 10 degree is 1.1% over 2.5–16 ${{\mu }}\text{m}$ . These characteristics indicate the integrated stealth functionality against active (laser) and passive (thermal) detection, respectively. The contact angle between the cloak and water is 154°, which also indicates its unique cross-media response capability. We also show that the developed infrared stealth cloak is robust to practical (nonideal) manufacturing conditions. Our design strategy expands the concept of infrared stealth to cross-media applications.

Transparent electromagnetic devices have received extensive attention in the development of large-aperture transparent antenna arrays for smart cities and optoelectronic co-aperture integrated wireless communication. As the key component of transparent antenna arrays, an optically transparent microwave power divider that requires conductive films with various sheet resistances for high transmission and low mutual coupling still remains challenges in practical realization. Here, we experimentally demonstrate a high-performance optically transparent eight-channel Wilkinson power divider by heterogeneously integrated low-loss metal mesh and high-loss indium tin oxide (ITO). Over the radio frequency band from 1.7 to 2.5 GHz (the center frequency is 2.1 GHz) and optical band from 380 to 760 nm, the isolation of the power divider is higher than 20 dB, the transparency is higher than 72%, and the transmission coefficient is around $-$ 9.6 to $-$ 10.7 dB. Our demonstration paves the way for future tunable transparent array antenna systems and optoelectronic co-aperture integrated multifunctional applications.

Introduction: Marine ferromanganese crusts are potentially important metal resources.The deep-ocean research and survey ships often need to carry out rapid chemical element component analysis of mineral resources, so as to plan for the geological resource exploration mission.Methods: The laser-induced breakdown spectroscopy can obtain the spectrum of chemical elements by the plasma excited by high-energy laser irradiation on the surface of the sample. A laser induced breakdown spectroscopy optical system for the detection of deepocean ferromanganese crusts is designed and built, which can meet the requirements of near-insitu chemical component detection of deep-ocean mineral resources on ocean-going survey ships.Results: Hyperspectral data of Fe-Mn crusts are carried out by the Laser-induced breakdown spectroscopy (LIBS) system during a deep-sea exploration mission at a depth of 2,490 m in the South China Sea. The experimental parameters of laser energy and spectral acquisition delay are optimized to improve the spectral measurement accuracy. Based on the calibration-free method, the significant spectral features of the chemical elements Fe and Mn were obtained through proper alignment with the National Institute of Standards and Technology (NIST) chemical element spectral library.Discussion: The LIBS instrument can be placed on board long-range survey vessels in the future to provide a fast, convenient, accurate, and economical detection method for deep-ocean resource exploration.

This report proposes an athermalization and achromatization method based on combined glasses and comprehensive distance weight to select and replace optical and housing tube materials quantitatively without multiple iterations. In addition, it presents a new achromatic and athermal condition of the replacement search method using combined glasses. It establishes an athermal glass map model combining the cluster center, tube materials, two combined lenses, and a rest equivalent lens to analyze the characteristics of the glass distribution. A cluster analysis method was introduced to analyze the distribution characteristics of the athermal glass map in the visible catalog. The athermal ability of the housing tube and the replacement of combined glass material are evaluated by distance weight in athermal glass map. A complex aerial multiple lenses system was designed using this method and maintained high imaging quality from –40 °C to 70 °C. This method can reduce the number of iterations for the selection of combined glass and significantly improves the optimization efficiency of athermalization.

This paper proposes a polarization-sensitive, metal-dielectric-metal (MDM) subwavelength grating structure based on surface plasmon resonance that achieves wide-angle, narrow-band, and high absorption in the long-infrared region. The resonance characteristics of the MDM structure, excited by magnetic resonance (MR), cause the transverse magnetic (TM) and transverse electric (TE) modes to polarize. A model of the inductor capacitor (LC) circuit is also presented. Structural simulations demonstrate a near-perfect absorption characteristic (99.99%) at 9 µm center wavelength. For TM polarization with incident angles ranging from 0° to 89°, the MDM grating structure produced absorption rates over 90%, 81%, and 71% for incident angles of 66°, 73°, and 77°, respectively. The absorption peaks in the long-wave infrared band can be adjusted by varying the duty cycle or period, without adjusting structural parameters. The spectral absorption curve shows a red shift and maintains high absorption, with wide-angle and narrow-band, across various azimuth angles (0–90°), during an increase in duty cycle or period. This method reduces the difficulty and complexity of micro-nano processing, and enables multiple absorbers in the long-infrared band (7.5–13 µm) to be processed and prepared on the same substrate surface.

An alignment tolerance allocation and alignment method of orthogonal reflectors with high polarization-maintaining characteristics is presented. A geometric optics vector model of orthogonal reflectors is established to derive the propagation vector of the output beam, including pitch angle error of the first mirror, the side-scanning angle of the galvanometer, and rotation angle error of the secondary mirror. The polarization transmission matrix of the orthogonal reflectors is derived based on the 3D polarization ray-tracing algorithm to present the relationship between assembly errors and diattenuation or retardance of the orthogonal reflectors. A calculation example of certain polarization ellipticity error is given to quantitatively distribute the orthogonal mirror assembly error. The optimal side-sway angle selection method of the galvanometer side-sway angle in a laser communication system is presented; further, effective measures to minimize the polarization ellipticity error is put forward.