Hyperspectral imaging in ultralow-light conditions remains challenging due to the low signal-to-noise ratio. To address this challenge, we developed an ultralow-light hyperspectral imaging system that combines broadband Fabry-Perot spectral modulation with single-photon detection. We introduced a spectral-spatial dual-domain attention network to enhance spectral accuracy and provide fine-grained high-resolution information by capturing long-range spectral dependencies and achieving 2 & times; spatial upsampling. To ensure consistency with real physical imaging processes, we simulated a low-light hyperspectral dataset across 28 wavelength channels from 450 to 650 nm at 0.3 lux. Experiments on multiple macroscopic scenes and fluorescent microspheres validate that the proposed method can achieve high spectral fidelity, providing a reliable solution for hyperspectral imaging in low-light conditions. (c) 2026 Chinese Laser Press

Light carries high-dimensional information such as spectrum and polarization, but conventional photodetectors measure only intensity, making snapshot acquisition of multiple optical dimensions difficult. Here, we report a multidimensional on-chip optical imaging (MOCI) architecture comprising three functional layers, including a multidimensional encoding layer to encode incident light, an image acquisition layer to collect coupled intensity measurements, and a computing layer to recover multidimensional images from a snapshot measurement. Following this architecture, we developed an on-chip polarization-hyperspectral imaging (PHI) sensor operating at 74 frames s-1 with 2048  × 2448 pixels, 61 visible-to-near-infrared spectral channels, and four polarization states. The sensor acquires spectral and polarization signatures simultaneously in complex environments, enabling polarization-enhanced hyperspectral imaging through haze, suppression of reflection and glare, and hyperspectral 3D modeling with normal and height maps. This compact, on-chip, and high-throughput sensor provides a route to integrated snapshot multidimensional imaging and machine perception under challenging optical conditions.

Rolling bearings are critical components in rotating machinery, and their fault diagnosis helps reduce maintenance costs while ensuring reliable operation of the entire system. Addressing the limitations of conventional electrical vibration sensors—including susceptibility to electromagnetic interference, large size, and difficulty in achieving multi-axis monitoring within compact electromechanical equipment—this paper introduces a vibration sensing scheme based on a miniaturized triaxial fiber Bragg grating (FBG) sensor. To address the storage and computational challenges from long-term monitoring data while improving diagnostic accuracy and efficiency, a sparse Fourier transform and axis-fusion Mamba (SFT-AFM) network is proposed. The SFT module compresses high-frequency vibration signals into three-channel frequency–time heatmaps via Top-K sparse spectrum selection and sliding window processing, preserving salient fault-related spectral components. The AFM model employs an axis-fusion mechanism to capture sample-adaptive inter-axis feature correlations, utilizes a lightweight Mamba backbone to capture long-range spatiotemporal dependencies with linear complexity, and incorporates Instance-Batch Normalization (IBN-A) residual blocks to improve cross-condition stability, supporting fault feature extraction and classification. Experiments were conducted using a bearing vibration dataset acquired by triaxial FBG and triaxial piezoelectric sensors, which includes seven bearing states, five rotational speeds from 500 to 2500 rpm, and two load levels (0 and 1 N⋅m). Under −6 dB additive white Gaussian noise, SFT-AFM achieved a classification accuracy of 84.18%, outperforming the strongest baseline Attention (73.98%). The AFM model contains only 0.15 M parameters and occupies 0.58 MB in FP32 format. These results show that SFT-AFM combines compact parameter and storage footprints with excellent diagnostic performance under severe noise.

The subaperture stitching interferometry can extend the dynamic range of the interferometer and is widely used for high-resolution measurement of large-aperture, high-slope aspheres. Most subaperture stitching interferometry requires a high-precision multi-axis motion control system and a vibration-free environment. This paper proposes a polarization grating-based circular subaperture stitching interferometer assisted by a virtual-real combination algorithm to realize non-null measurement insensitive to vibration and alignment error. A polarization grating that scans subapertures through its axial rotation is adopted in place of the multi-axis motion control system. Polarization phase-shifting interferometry is introduced to achieve transient measurement of a single subaperture. Compared with traditional subaperture stitching interferometers, the proposed system is more compact and reduces measurement errors introduced by mechanical adjustments, improving the insensitivity to the vibration of individual subaperture measurements. Additionally, a virtual-real combination algorithm effectively suppresses retrace errors, reduces the impact of alignment errors on measurement accuracy, improves the overall insensitivity to vibration of subaperture stitching, and avoids positioning and calculation errors caused by complex stitching algorithms. The feasibility of the system and method, as well as their merits in insensitivity to vibration and large alignment tolerance, are verified through experiments. This research provides innovative and instructive insights into the application of polarization grating-based circular subaperture stitching interferometers.

The single nondestructive testing (NDT) techniques face the problem of low resolution when simultaneously detecting different types and locations of defects. Composite inspection methods, which combine different NDT techniques, have been widely studied due to their high defect detection accuracy. However, most of the existing composite detection methods require complex sensor systems or rely on complex signal-processing algorithms. Therefore, this article proposes a novel hybrid sensor based on the electromagnetic acoustic transducer (EMAT) and the magnetic flux leakage (MFL) mechanism, which allows to accurately detect defects in ferromagnetic materials. This hybrid sensor employs a straightforward EMAT-MFL configuration, which only requires a single permanent magnet to generate the requisite magnetic field for the EMAT and MFL sensor components. In addition, it adopts a unique orthogonal butterfly coil design for the detection of cracks. The obtained results show a significant frequency difference between the EMAT and MFL signals, which demonstrates their independence and lack of interference. This eliminates the potential issue of signal aliasing decoupling. The hybrid sensor can fully use the advantages of the EMAT and MFL technologies to simultaneously detect defects and cracks on the top and bottom surfaces of ferromagnetic materials. Furthermore, the wall thinning defects can be detected with a maximum detection error of only 4.48%. This article proposes a feasible approach for miniaturizing hybrid sensors and increasing their detection performance.

Developing and integrating advanced image sensors with novel algorithms in camera systems is prevalent with the increasing demand for computational photography and imaging on mobile platforms. However, the lack of high-quality data for research and the rare opportunity for in-depth exchange of views from industry and academia constrain the development of mobile intelligent photography and imaging (MIPI). To bridge the gap, we introduce the first MIPI challenge including five tracks focusing on novel image sensors and imaging algorithms. In this paper, RGBW Joint Fusion and Denoise, one of the five tracks, working on the fusion of binning-mode RGBW to Bayer at half resolution is introduced. The participants were provided with a new dataset including 70 (training) and 15 (validation) scenes of high-quality RGBW and Bayer pair. In addition, for each scene, RGBW of 24 dB and 42 dB are provided. All the data were captured using a RGBW sensor in both outdoor and indoor conditions. The final results are evaluated using objective metrics including PSNR, SSIM [ 11 ], LPIPS [ 15 ] and KLD. A detailed description of all models developed in this challenge is provided in this paper. More details of this challenge and the link to the dataset can be found in https://github.com/mipi-challenge/MIPI2022

This paper presents a polarization grating based circular subaperture stitching interferometer. The system can be used for small F/# concave surface tests with a large F/# transmission sphere, where F/# is the ratio of focal length to aperture. A polarization grating was employed to deflect the incident beam for subaperture scanning by its axial rotation instead of a multi-axis motion-control system. Compared with the traditional subaperture stitching interferometric system, the system proposed in this paper is smaller in size and reduces the measurement error introduced by mechanical adjustment. Using a virtual interferometer model and a virtual–real combination algorithm to remove the retrace error, the full-aperture figure error can be directly obtained without the need for a complex stitching algorithm. The feasibility of the algorithm was verified, and the measurement error caused by the modeling error was analyzed by simulation. The capability of the polarization grating to scan subapertures was experimentally confirmed, and possible solutions to some engineering challenges were pointed out. The research in this paper has pioneering and guiding significance for the application of polarization grating in interferometry.

Large optical flats play a remarkable role in advanced large-aperture optical systems and the testing of the surface shape error is indispensable for the fabrication. The widely adopted Ritchey-Common test for large optical flats will fail without the rigorous test configurations including a large F/# prerequisition and a flat-to-interferometer distance invariance. A virtual-real combination Ritchey-Common interferometry is proposed to avoid the large F/# prerequisition by accurately modelling the optical path in a virtual interferometer. Furthermore, a virtual-real combination iterative algorithm is proposed in this method to break the flat-to-interferometer distance invariance. Measurement experiments for 100 mm and 422 mm aperture flats were performed to demonstrate the feasibility of this method. Compared with a direct testing in a standard Zygo interferometer, the peak to valley (PV) and root mean square (RMS) errors were less than 0.1 λ and 0.01 λ (λ=632.8 nm), respectively, in different Ritchey angles and flat-to-interferometer distances. Further numerical simulations demonstrate that RMS errors for various Zernike aberrations in arbitrary F/# are less than 0.01 λ. This method can break the distance invariance restriction and achieve high accuracy with an arbitrary F/#, thus providing substantial freedom in the design of test configurations to accommodate various test scenarios.

Covalent organic frameworks (COFs) are two-dimensional or three-dimensional organic crystalline materials with nanoscale structural order, which have structural advantages such as high periodicity and modifiability. Electrochemical biosensors based on COFs have the characteristics of ultra-sensitivity, strong specificity, and good repeatability, and have broad prospects in the detection of biological samples. The synthesis methods and strategies of COFs, the introduction and classification of electrochemical biosensors, and the application of COFs in electrochemical biosensing to detect biological samples are briefly summarized. Finally, the technical bottlenecks of COFs materials in the field of biosensing and their future development directions are summarized and discussed.

In AR and VR devices, freeform surfaces are widely used to improve system performance. The manufacture of freeform surfaces is limited to the measurement. In order to guide the manufacturing process, we have proposed a real-time interferometric measurement system. In the system, an accurate, automatic and fast description method is needed to describe complex freeform surface. In order to improve this situation, a description method with automatically configurable Gaussian radial basis function (AC-GRBF) has been proposed. The key parameters of AC-GRBF, the number of subapertures N, coefficient A and the base number of GRBFs affect the fitting accuracy and speed, and they are analyzed by numerical simulation in the paper. The analysis in this paper can provide reference for the description method of GRBF, especially AC-GRBF, and the description of complex freeform surfaces in the design.

This paper proposes an interferometry method based on a fixed interferometer structure and locally compensated stitching. The subaperture measurement is completed by applying a double-optical-wedge compensator in the "rugged" area of the surface that cannot be measured. The data of the measured area is stitched to obtain the local surface shape. The calibration of the double-optical-wedge compensator is performed by using a standard mirror. Surface figure error (SFE) of the standard mirror is measured by an interferometer beforehand. Compared with the SFE measured after adding the compensator in the optical path, the phase and aberration of the double-optical-wedge can be obtained. Measured data is processed by the subaperture stitching algorithm. Through the weighted fusion algorithm, the corresponding data values on the overlapping areas are weighted, and different weights are assigned to different areas to make the stitching transition smooth. Based on the principle of interferometry, a double-optical-wedge compensation measurement system is designed and implemented. A simulation model of the measurement experiment is presented, and the validity of the method is verified by simulation.

Computer-generated hologram (CGH) method is a high-precision aspherical surface detection method. CGH produces wavefronts of any shape with extremely high precision and is adopted in null test. Liquid crystal CGH (LC-CGH) is a new type of CGH with short production cycle and low cost. It is a promising alternative to traditional CGH. In this paper, the overall process flow of LC grating preparation is presented. The influences of three process parameters, such as LC solution concentration, spin coating speed and time on the three physical quantities of LC grating diffraction efficiency, LC polymer film thickness and phase delay are studied. Based on the analysis, improvement measures are proposed for the preparation process. The research carried out in this paper has guiding significance for the processing and manufacturing of LC-CGH.

We propose a liquid crystal (LC) hologram fabricated with photoalignment technology, for the measurement of a cylindrical surface. A standard cylindrical surface reflects the incident planar wavefront and generates an interferogram with a planar reference wavefront. Photoalignment azo-dye material is then exposed by the interferogram and aligned with desired orientations, following with depositing LC monomer to generate the designed phase information. After ultra-violet curing, the fabricated LC hologram plate can generate a standard cylindrical wavefront when illuminated with a planar wavefront. The minimal line-width due to the limitation of LC molecules is sub-microns, which is smaller than the limitation in traditional CGH. The systematic design of the measurement is proposed, followed by a demonstration simulation.

MEMS processing technology can manufacture any complex structures in a plane, using this point, a variable stiffness design idea for the planar micro-spring is proposed. That is, using one type of structure named contact pairs to achieve stiffness change during the micro-spring’s stretching process. Using contact pairs, three types of variable stiffness springs are designed: stiffness increase spring, stiffness decrease spring and stiffness hump spring. Finally, the variable stiffness springs’ application for fuze setback arming device is discussed. When the three types of springs are used in setback arming device, the stiffness decrease spring is better than the other two springs from security analysis. Kinematic analysis shows that, if the variable stiffness spring’s design is reasonable, the setback arming device not only can effectively solve the safety and reliability issues for rocket fuze, but also applies in small caliber grenade fuze’s working environment without changing the setback arming device’s size and structure. Analysis result indicate that the setback arming device based on MEMS variable stiffness spring is universal for rocket fuze and small caliber grenade fuze.

A white-light interferometry based on the Fourier transform method is proposed to measure the optical path difference (OPD) of the high-finesse fiber optic extrinsic Fabry-Perot interferometric (EFPI) sensor. The Fourier spectrum of the transmission spectrum signal consists of multiple frequency components because of the multiple-beam interference occurring in the high-finesse EFPI sensor. The high-order frequency component of the Fourier spectrum can be extracted by the Fourier transform method to recover the OPD in order to overcome the spectrum overlapping, which happens when the OPD of the EFPI sensor is short. In the experiment, a high-finesse fiber optic EFPI sensor with the cavity length of 120 mu M is measured, and the second-order frequency component was extracted to recover the cavity length. The standard deviation of the measurement results was 9.132 nm. The measurement range of the Fourier transform method was effectively extended to the short OPD.

An in-line photonic crystal fibre-based Mach–Zehnder interferometer (PCF-MZI) with temperature compensation has been proposed and experimentally demonstrated. The in-line PCF-MZI is fabricated by splicing a section of photonic crystal fibre between two single mode fibers. The temperature compensation of the in-line PCF-MZI is realized by using materials with proper thermal expansion coefficients. The device possesses the temperature insensitive feature, and a temperature stability of 1.0 pm °C−1 has been experimentally demonstrated with the packaging material of ceramic.

The measurement of the diameter change of a piezoelectric transducer (PZT) cylinder with the white-light interferometry is proposed and experimentally demonstrated. One arm of a Mach–Zehnder interferometer (MZI) is wrapped on the PZT cylinder, and the phase change of the interferogram of the MZI is used to determine the diameter change when a DC voltage is applied on the PZT cylinder. The Fourier transform white-light interferometry is used for recovering the phase change of the interferometer. The experimental results show that the diameter change resolution of 0.8nm for the PZT cylinder with diameter of 40mm is achieved.

A fiber optic white-light interferometry based on cross-correlation calculation is presented. The detected white-light spectrum signal of fiber optic extrinsic Fabry-Perot interferometric (EFPI) sensor is firstly decomposed by discrete wavelet transform for denoising before interrogating the cavity length of the EFPI sensor. In measurement experiment, the cross-correlation algorithm with multiple-level calculations is performed both for achieving the high measurement resolution and for improving the efficiency of the measurement. The experimental results show that the variation range of the measurement results was 1.265 nm, and the standard deviation of the measurement results can reach 0.375 nm when an EFPI sensor with cavity length of 1500 μm was interrogated.

A novel method for the measurement of chromatic dispersion (CD) profiles of photonic crystal fibers (PCFs) by using a tip interferometer is presented. A PCF tip interferometer is formed by splicing a short section of the PCF to a single mode fiber. The CD coefficient of the PCF is measured from 1525 to 1565 nm by using the white-light interferometry. The result of the proposed method agrees with that of the conventional swept wavelength interferometry. The maximum variation is only 0.084 ps/nm·km at the wavelength of 1537.672 nm.

In order to quickly and exactly detect the subpixel image edge of micro-part, a fast subpixel edge detection method based on the property of Gaussian blurred edge model is proposed. Firstly, the approximate positioning of edge point was extracted by double-threshold segmentation; secondly a Zernike moment operator with a mask size of 5×5 was used to get rid of false edge points and relocate the edge with subpixel accuracy. Experiment results show that the subpixel accuracy and the running time of the method are 0.16 pixel and 0.94s. Therefore, the method is suitable for online threedimensional size detection of micro-part.