To improve the low-frequency isolation performance of optical platforms, an electromagnetic active-negative-stiffness generator (EANSG) was proposed, using nano-resolution laser interferometry sensors to monitor the micro-vibration of an optical platform, and precision electromagnetic actuators integrated with a relative displacement feedback strategy to counteract the positive stiffness of pneumatic springs within a micro-vibration stroke, thereby producing high-static-low-dynamic stiffness characteristics. The effectiveness of the method was verified by both theoretical and experimental analyses. The experimental results show that the vertical natural frequency of the optical platform was reduced from 2.00 to 1.37 Hz, the root mean square of displacement was reduced from 1.28 to 0.69 μm, and the root mean square of velocity was reduced from 14.60 to 9.33 μm/s, proving that the proposed method can effectively enhance the low frequency isolation performance of optical platforms.

Micro-computed tomography (micro-CT) is a widely used state-of-the-art instrument employed to study the morphological structures of objects in various fields. However, its small field-of-view (FOV) cannot meet the pressing demand for imaging relatively large objects at high spatial resolutions. Recently, we devised a novel scanning mode called multiple source translation CT (mSTCT) that effectively enlarges the FOV of the micro-CT and correspondingly developed a virtual projection-based filtered backprojection (V-FBP) algorithm for reconstruction. Although V-FBP skillfully solves the truncation problem in mSTCT, it requires densely sampled projections to arrive at high-resolution reconstruction, which reduces imaging efficiency. In this paper, we develop two backprojection-filtration (BPF)-based algorithms for mSTCT—S-BPF (derivatives along source) and D-BPF (derivatives along detector). D-BPF can achieve high-resolution reconstruction with fewer projections than V-FBP and S-BPF. Through simulated and physical experiments conducted in this paper, we demonstrate that D-BPF can dramatically reduce the number of projection views compared with V-FBP at the same spatial resolution, which makes mSTCT more feasible in practice. Meanwhile, S-BPF can yield more stable results than D-BPF, which is similar to V-FBP.

An enhanced circulating cooling water (CCW) machine is developed to simultaneously achieve high temperature stability and dynamic performance of CCW temperature control. Dynamic thermal filtering based on an auto-updatable thermal capacity medium is proposed to reduce the temperature fluctuation of the CCW. Agile thermal control is presented to realize a quick response and high resolution of temperature control, through thermal inertia minimization and bidirectional regulation of heating/cooling power. Experimental results indicate that a temperature stability of ±3 mK (peak to peak value) and a settling time of 128 s, corresponding to a 1 K step set value, are achieved. It can therefore be concluded that the developed machine can satisfy the challenging requirements of precision manufacturing.

A discrete fringe phase unwrapping algorithm (DFPUA) based on Kalman motion estimation is proposed to accurately demodulate the phases of I/Q-interferometers with deeply under-sampled quadrature signals, thus to break through the limitations of the Nyquist frequency for high-speed measurement. The basic concept of DFPUA is to estimate the current displacement according to the former motion state, then confirm the actual phase integer number by comparing the estimated phase decimal with the actual phase decimal; in this way, peak acceleration/jerk instead of peak velocity becomes the factor that determines the sampling rate. Two types of DFPUA including velocity estimation and velocity-acceleration estimation are illustrated in detail. Simulation experiment results indicate that the DFPUA realizes a significant reduction in the sampling rate and the amount of data for low frequency vibration measurement, proposing a practical approach for high-speed and long-time measurement such as ultra-low frequency vibration calibration.

Recently, in some special situations, linear computed tomography (LCT) systems have provided better imaging solutions for internal structures compared with conventional CT instruments. To image the region of interest (ROI) and weaken projection truncation in the LCT reconstruction, the backprojection filtration (BPF) algorithm is an effective solution; however, in BPF for LCT, it is difficult to achieve stable interior reconstruction, and for differentiated backprojection (DBP) images of LCT. To satisfy multiple reconstruction scenarios for LCT, including interior ROI, complete object, and exterior region, we propose two types of reconstruction architectures. The first overlays multiple DBP images to obtain a complete DBP image and then uses a network to learn the overlying or composite Hilbert filtering function, referred to as the overlay-single network (OSNet). The second uses multiple networks to train different directional Hilbert filtering models for DBP images of multiple linear scanning trajectories, respectively, and then overlays the reconstructed results, i.e., multiple networks overlaying (MNetO). In two architectures, we introduce a Swin transformer (ST) block to the generator of pix2pixGAN to extract both local and global features from DBP images at the same time. We investigate the proposed architectures from different networks, FOV sizes, pixel sizes, number of projections, geometric magnification, and computation time. The two architectures are proven to recover images. OSNet outperforms BPF in multiple scenarios. In OSNet, ST-pix2pixGAN is superior to pix2pixGAN and CycleGAN for the different networks. The average peak signal-to-noise ratio (PSNR) value reaches 41.1949 dB, which improves by 31% compared to BPF. The average structural similarity index measure (SSIM) and root-mean-square error (RMSE) are improved at 0.9996 and 0.0093, respectively. In MNetO, one model in a certain direction can increase the PSNR by about 18.4% compared to BPF, enabling high-quality imaging of the exterior edge. Our architectures can provide great solutions or references for LCT high-resolution imaging and nondestructive measuring.