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Remote Sensing and Sensors|34 Article(s)
Three-dimensional coherent ladar based on FMCW and its flight demonstration
Zhiyong Lu, Wei Lu, Yu Zhou, Jianfeng Sun, Qian Xu, and Lijuan Wang
A scanning three-dimensional coherent laser radar (ladar) based on the frequency modulated continuous wave (FMCW) is proposed and demonstrated, which can obtain many three-dimensional high-quality images. The system utilizes an electro-optic modulator and an optical filter to output a linear FMCW with a bandwidth of 2 GHz. The flexible and variable rotating double prism is used for beam scanning. The images of flight demonstration are formed by attitude compensation correction. The experiment result validates the performance of our system for airborne three-dimensional scanning imaging. A scanning three-dimensional coherent laser radar (ladar) based on the frequency modulated continuous wave (FMCW) is proposed and demonstrated, which can obtain many three-dimensional high-quality images. The system utilizes an electro-optic modulator and an optical filter to output a linear FMCW with a bandwidth of 2 GHz. The flexible and variable rotating double prism is used for beam scanning. The images of flight demonstration are formed by attitude compensation correction. The experiment result validates the performance of our system for airborne three-dimensional scanning imaging.
Chinese Optics Letters
- Publication Date: Sep. 10, 2019
- Vol. 17, Issue 9, 092801 (2019)
Theoretical study on negative permittivity of the material producing sharp surface plasmon resonance dips
Dejing Gong, Yinquan Yuan, Lei Liang, and Minghong Yang
Using theoretical simulations for optical fiber surface plasmon resonance (SPR) sensors and prism-based SPR sensors coated with negative permittivity material (NPM), we investigated the effect of the permittivity of NPM on the transmitted spectrum of optical fiber SPR sensors and the reflected spectrum of prism-based SPR sensors and then obtained optimum permittivity of the NPM, which can excite the sharpest SPR spectrum in the white light region (400–900 nm). Using theoretical simulations for optical fiber surface plasmon resonance (SPR) sensors and prism-based SPR sensors coated with negative permittivity material (NPM), we investigated the effect of the permittivity of NPM on the transmitted spectrum of optical fiber SPR sensors and the reflected spectrum of prism-based SPR sensors and then obtained optimum permittivity of the NPM, which can excite the sharpest SPR spectrum in the white light region (400–900 nm).
Chinese Optics Letters
- Publication Date: Apr. 10, 2019
- Vol. 17, Issue 4, 042801 (2019)
Ultra-high range resolution demonstration of a photonics-based microwave radar using a high-repetition-rate mode-locked fiber laser
Shaofu Xu, Weiwen Zou, Guang Yang, and Jianping Chen
We experimentally demonstrate the ultra-high range resolution of a photonics-based microwave radar using a high repetition rate actively mode-locked laser (AMLL). The transmitted signal and sampling clock in the radar originate from the same AMLL to achieve a large instantaneous bandwidth. A Ka band linearly frequency modulated signal with a bandwidth up to 8 GHz is successfully generated and processed with the electro-optical upconversion and direct photonic sampling. The minor lobe suppression (MLS) algorithm is adopted to enhance the dynamic range at a cost of the range resolution. Two-target discrimination with the MLS algorithm proves the range resolution reaches 2.8 cm. The AMLL-based microwave-photonics radar shows promising applications in high-resolution imaging radars having the features of high-frequency band and large bandwidth. We experimentally demonstrate the ultra-high range resolution of a photonics-based microwave radar using a high repetition rate actively mode-locked laser (AMLL). The transmitted signal and sampling clock in the radar originate from the same AMLL to achieve a large instantaneous bandwidth. A Ka band linearly frequency modulated signal with a bandwidth up to 8 GHz is successfully generated and processed with the electro-optical upconversion and direct photonic sampling. The minor lobe suppression (MLS) algorithm is adopted to enhance the dynamic range at a cost of the range resolution. Two-target discrimination with the MLS algorithm proves the range resolution reaches 2.8 cm. The AMLL-based microwave-photonics radar shows promising applications in high-resolution imaging radars having the features of high-frequency band and large bandwidth.
Chinese Optics Letters
- Publication Date: Jun. 10, 2018
- Vol. 16, Issue 6, 062801 (2018)
Far-field outdoor experimental demonstration of down-looking synthetic aperture ladar
Guangyuan Li, Zhiyong Lu, Yu Zhou, Jianfeng Sun, Qian Xu, Chenzhe Lao, Hongyu He, Guo Zhang, and Liren Liu
A specific system structure of down-looking synthetic aperture imaging ladar (SAIL) is given, and a far-field experiment over 6 km of down-looking SAIL under this system design is carried out. The down-looking SAIL can overcome the influence of atmospheric turbulence to a great extent. By applying this system design, it also has advantages in self-compensating phase modulation. A fine image is obtained after aligning in the orthogonal direction and phase error compensation in the travel direction based on a dominant scatterer. The achieved imaging resolutions in the two dimensions are both better than 5 cm. A specific system structure of down-looking synthetic aperture imaging ladar (SAIL) is given, and a far-field experiment over 6 km of down-looking SAIL under this system design is carried out. The down-looking SAIL can overcome the influence of atmospheric turbulence to a great extent. By applying this system design, it also has advantages in self-compensating phase modulation. A fine image is obtained after aligning in the orthogonal direction and phase error compensation in the travel direction based on a dominant scatterer. The achieved imaging resolutions in the two dimensions are both better than 5 cm.
Chinese Optics Letters
- Publication Date: Aug. 10, 2017
- Vol. 15, Issue 8, 082801 (2017)
Efficient multi-bands image compression method for remote cameras
Jin Li, Fengdeng Liu, and Zilong Liu
In this Letter, we propose an efficient compression algorithm for multi-spectral images having a few bands. First, we propose a low-complexity removing spectral redundancy approach to improve compression performance. Then, a bit plane encoding approach is applied to each band to complete the compression. Finally, the experiments are performed on multi-spectral images. The experiment results show that the proposed compression algorithm has good compressive property. Compared with traditional approaches, the proposed method can decrease the average peak signal noise ratio by 0.36 dB at 0.5 bpp. The processing speed reaches 23.81 MPixels/s at the working frequency of 88 MHz, which is higher than the traditional methods. The proposed method satisfies the project application. In this Letter, we propose an efficient compression algorithm for multi-spectral images having a few bands. First, we propose a low-complexity removing spectral redundancy approach to improve compression performance. Then, a bit plane encoding approach is applied to each band to complete the compression. Finally, the experiments are performed on multi-spectral images. The experiment results show that the proposed compression algorithm has good compressive property. Compared with traditional approaches, the proposed method can decrease the average peak signal noise ratio by 0.36 dB at 0.5 bpp. The processing speed reaches 23.81 MPixels/s at the working frequency of 88 MHz, which is higher than the traditional methods. The proposed method satisfies the project application.
Chinese Optics Letters
- Publication Date: Feb. 10, 2017
- Vol. 15, Issue 2, 022801 (2017)
Photonics-based real-time and high-resolution ISAR imaging of non-cooperative target|Editors' Pick
Fangzheng Zhang, Qingshui Guo, Ying Zhang, Yao Yao, Pei Zhou, Daiyin Zhu, and Shilong Pan
Real-time and high-resolution imaging is demonstrated based on field trial detection of a non-cooperative target using a photonics-based inverse synthetic aperture radar (ISAR). By photonic generation and de-chirping of broadband linear frequency modulation signals, the radar can achieve a high range resolution thanks to the large instantaneous bandwidth (8 GHz at the K band), as well as real-time ISAR imaging using low-speed analog-to-digital conversion (25 MSa/s). A small-size unmanned aerial vehicle is employed as the non-cooperative target, and ISAR imaging is realized with a resolution far better than those achieved by the previously reported photonics-based ISARs. The capability for real-time ISAR imaging is also verified with an imaging frame rate of 25 fps. These results validate that the photonics-based radar is feasible in practical real-time and high-resolution ISAR imaging applications. Real-time and high-resolution imaging is demonstrated based on field trial detection of a non-cooperative target using a photonics-based inverse synthetic aperture radar (ISAR). By photonic generation and de-chirping of broadband linear frequency modulation signals, the radar can achieve a high range resolution thanks to the large instantaneous bandwidth (8 GHz at the K band), as well as real-time ISAR imaging using low-speed analog-to-digital conversion (25 MSa/s). A small-size unmanned aerial vehicle is employed as the non-cooperative target, and ISAR imaging is realized with a resolution far better than those achieved by the previously reported photonics-based ISARs. The capability for real-time ISAR imaging is also verified with an imaging frame rate of 25 fps. These results validate that the photonics-based radar is feasible in practical real-time and high-resolution ISAR imaging applications.
Chinese Optics Letters
- Publication Date: Nov. 10, 2017
- Vol. 15, Issue 11, 112801 (2017)
Millimeter-wave emission characteristics of bilayer radar-infrared compound stealth material
Yayun Cheng, Fei Hu, Feng He, Liang Wu, and Xiaoqin He
To achieve radar and infrared stealth, an infrared stealth layer is usually added to the radar absorbing material (RAM) of stealth aircraft. By analyzing the millimeter-wave (MMW) emissivities of three stealth materials, this Letter investigates the impact of the added infrared stealth layer on the originally “hot” MMW emission of RAM. The theoretical and measured results indicate that, compared with the monolayer RAM, the MMW emission of the bilayer material is still strong and its emissivity is reduced by 0.1–0.2 at almost every incident angle. The results partially demonstrate the feasibility of detecting stealth aircraft coated with this bilayer stealth material. To achieve radar and infrared stealth, an infrared stealth layer is usually added to the radar absorbing material (RAM) of stealth aircraft. By analyzing the millimeter-wave (MMW) emissivities of three stealth materials, this Letter investigates the impact of the added infrared stealth layer on the originally “hot” MMW emission of RAM. The theoretical and measured results indicate that, compared with the monolayer RAM, the MMW emission of the bilayer material is still strong and its emissivity is reduced by 0.1–0.2 at almost every incident angle. The results partially demonstrate the feasibility of detecting stealth aircraft coated with this bilayer stealth material.
Chinese Optics Letters
- Publication Date: Jun. 10, 2016
- Vol. 14, Issue 6, 062802 (2016)
Combination of differential discrimination and direct discrimination in pulsed laser time-of-flight systems
Dongxian Geng, Xing Fu, Pengfei Du, Wei Wang, and Mali Gong
The output amplitude of the differential circuit is studied for differential discrimination in pulsed laser time-of-flight systems. Based on the studies of the probability of detection and the probability of false alarms, the minimum detectable input signal of differential discrimination can be calculated. The results indicate that the differential discrimination detectability of the small signal will be reduced. A combined discrimination is proposed in this Letter to improve the time resolution of the large signal and ensure the probability of detection of the small signal at the same time. A proper value of the circuit parameter is found to balance the time resolutions of the small and large signals. The output amplitude of the differential circuit is studied for differential discrimination in pulsed laser time-of-flight systems. Based on the studies of the probability of detection and the probability of false alarms, the minimum detectable input signal of differential discrimination can be calculated. The results indicate that the differential discrimination detectability of the small signal will be reduced. A combined discrimination is proposed in this Letter to improve the time resolution of the large signal and ensure the probability of detection of the small signal at the same time. A proper value of the circuit parameter is found to balance the time resolutions of the small and large signals.
Chinese Optics Letters
- Publication Date: Jun. 10, 2016
- Vol. 14, Issue 6, 062801 (2016)
Detection performance of trigger-controlled Geiger-mode avalanche photodiodes in weak optical signal detection
Peng Zhao, Yabo Yuan, Yan Zhang, and Weiping Qian
This Letter introduces a trigger-controlled Geiger-mode avalanche photodiode (GM-APD). A hierarchical look-back-upon tree recurrence method is given to predict the performance of trigger-controlled GM-APDs under different trigger-count upper limits. In addition, the normalized detection probability is defined to evaluate the detection performance of trigger-controlled GM-APDs in typical weak optical signal detection (impulse noise and continuous noise situations). Theoretical analyses show that the trigger-controlled GM-APD improves the detection performance of GM-APDs in weak optical signal detection via the optimization of the trigger-count upper limit, compared with single-trigger and multi-trigger GM-APDs. This Letter introduces a trigger-controlled Geiger-mode avalanche photodiode (GM-APD). A hierarchical look-back-upon tree recurrence method is given to predict the performance of trigger-controlled GM-APDs under different trigger-count upper limits. In addition, the normalized detection probability is defined to evaluate the detection performance of trigger-controlled GM-APDs in typical weak optical signal detection (impulse noise and continuous noise situations). Theoretical analyses show that the trigger-controlled GM-APD improves the detection performance of GM-APDs in weak optical signal detection via the optimization of the trigger-count upper limit, compared with single-trigger and multi-trigger GM-APDs.
Chinese Optics Letters
- Publication Date: Apr. 10, 2016
- Vol. 14, Issue 4, 042801 (2016)
Short-wave infrared signature and detection of aicraft in flight based on space-borne hyperspectral imagery
Yueming Wang, Feng Xie, and Jianyu Wang
Infrared signatures of aircraft are the basis for detection and monitoring. In past years, most of the studies focused on the aircraft’s infrared signature in the mid-wave spectral region and long-wave spectral region for missile guidance or aircraft survivability studies. For the security of civil aviation, methods and instruments that can detect and monitor aircrafts from space are expected to be developed in the coming years. A short-wave infrared hyperspectral imager aboard the Tiangong-1 spacecraft acquired some civil aircraft’s spectral data. The differences between the aircraft and the background in their spectral signatures are analyzed and discussed. Less absorption in the vapor absorption bands and a reflection spike is discovered at the 1.84 μm spectral band. The result shows that 1.84 μm and other vapor absorption bands can make contributions to aircraft detection in the daytime. Infrared signatures of aircraft are the basis for detection and monitoring. In past years, most of the studies focused on the aircraft’s infrared signature in the mid-wave spectral region and long-wave spectral region for missile guidance or aircraft survivability studies. For the security of civil aviation, methods and instruments that can detect and monitor aircrafts from space are expected to be developed in the coming years. A short-wave infrared hyperspectral imager aboard the Tiangong-1 spacecraft acquired some civil aircraft’s spectral data. The differences between the aircraft and the background in their spectral signatures are analyzed and discussed. Less absorption in the vapor absorption bands and a reflection spike is discovered at the 1.84 μm spectral band. The result shows that 1.84 μm and other vapor absorption bands can make contributions to aircraft detection in the daytime.
Chinese Optics Letters
- Publication Date: Dec. 10, 2016
- Vol. 14, Issue 12, 122801 (2016)
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