slow axis
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2020 ◽  
Vol 17 (11) ◽  
pp. 115603
Author(s):  
Alexander A Moiseev ◽  
Pavel A Shilyagin ◽  
Sergey Yu Ksenofontov ◽  
Dmitry A Terpelov ◽  
Tatyana V Vasilenkova ◽  
...  


2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Wanyan Sun ◽  
Yonghong Tan ◽  
Ruili Dong ◽  
Wenjiang Shen

In this paper, 10 resonant modes were divided based on the structure of a specific two-dimensional electromagnetic micromirror from Professor Shen’s team and Finite Element Method (FEM), and using as many as 10 resonant modes to do such analysis was the first time according to the best of our knowledge. The results showed that the slow axis can participate in several resonant motions under the signals of resonant frequencies. In particular, participating in Mode 1 for slow-scan axis was the key reason to the instability of Vertical Refreshing Scanning (VRS) in raster scanning. In addition, a piecewise PID control based on filters design for this electromagnetic micromirror was proposed to suppress the unexpected resonant oscillation and to improve the angular positioning accuracy in slow-scan axis control. Finally, the proposed method was applied to electromagnetic micromirror stages, and the experimental results showed that the proposed approach was reliable.



2020 ◽  
Author(s):  
Alexander A. Moiseev ◽  
Pavel A. Shilyagin ◽  
Sergey Yu. Ksenofontov ◽  
Dmitry A. Terpelov ◽  
Tatyana V. Vasilenkova ◽  
...  

The method for displacement correction along the slow axis of Optical Coherence Tomography (OCT) data volumes is presented. The method is based on the recursive replacement of the next displaced OCT measurements by the weighted summation of itself and the previous OCT measurement in the slow axis dimension already corrected for the displacement. The values of the appropriate weight multipliers were defined from the local correlation of the two measurements. The proposed method was used as a preprocessing step for Optical Coherence Angiography processing of the OCT data. Substantial reduction of the motion-induced stripe artifact was demonstrated.





2020 ◽  
Vol 47 (1) ◽  
pp. 0105002
Author(s):  
赵碧瑶 Zhao Biyao ◽  
井红旗 Jing Hongqi ◽  
仲莉 Zhong Li ◽  
曼玉选 Man Yuxuan ◽  
班雪峰 Ban Xuefeng ◽  
...  


Author(s):  
В.В. Дюделев ◽  
Д.А. Михайлов ◽  
В.Ю. Мыльников ◽  
А.В. Бабичев ◽  
С.Н. Лосев ◽  
...  

The near and far fields of quantum cascade lasers emitting in the spectral range near 8 µm have been studied. Lasing in the fundamental waveguide mode along the "fast" axis with a divergence of ~ 50º was observed in all samples of lasers with stripe widths of 22 and 50 µm in the entire range of pump currents. On the "slow" axis, multimode lasing and competition between the fundamental and higher waveguide modes were observed, which manifests itself for lasers with a 50 µm stripe in an increase of the radiation divergence from ~ 10º near the threshold to > 50º with a two-fold excess of the lasing threshold. The divergence along the slow axis for lasers with a stripe width of 22 µm remained unchanged over the entire range of pump currents and amounted to ~ 50º. The significant contribution of the fundamental mode to the total radiation intensity of quantum cascade lasers, being obvious from the far-field intensity distribution, cannot be established solely from the results of measurements of the near-field.



Sensors ◽  
2019 ◽  
Vol 19 (6) ◽  
pp. 1375 ◽  
Author(s):  
Chunfang Rao ◽  
Lingze Duan

Lamb wave (LW) is well suited for structural health monitoring (SHM) in advanced composites. However, characteristic differences between the symmetric modes and the anti-symmetric modes often add complexity to SHM systems. The anisotropic nature of composite materials, on the other hand, necessitates direction-sensitive sensing. In this paper we report the experimental demonstration of bidirectional (0° and 90°), bimodal (S0 and A0) LW measurement within the frequency range of 20–140 kHz using a polarization-maintaining fiber Bragg grating (PM-FBG) sensor attached to a composite laminated plate. By selectively interrogating the fast and/or the slow axis of the PM-FBG, we show that not only can the sensor respond to LWs propagating along both directions, but the response can also be used to differentiate the two directions. Moreover, the fast axis of the sensor is able to respond to both the S0 and the A0 modes when the sensor is aligned with the wave propagation direction, whereas single S0 mode response can be achieved with the slow axis operating perpendicularly to the wave propagation direction. Such diverse responses indicate the potential of PM-FBGs as versatile multi-parameter SHM detectors, which can effectively address the challenges posed by material anisotropicity and LW mode diversity.



2018 ◽  
Vol 45 (10) ◽  
pp. 1005004
Author(s):  
宋健 Song Jian ◽  
高欣 Gao Xin ◽  
闫宏宇 Yan Hongyu ◽  
张晓磊 Zhang Xiaolei ◽  
张哲铭 Zhang Zheming ◽  
...  


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