粗糙目標對光外差探測信號的退相干效應
發(fā)布時間：2018-08-10 17:11
【摘要】：光外差探測是公認的具有量子探測極限本領的相干探測體制,可以實現(xiàn)對回波信號振幅、頻率和相位攜帶信息的全息探測,在微弱信號探測方面,具有直接探測不可比擬的優(yōu)點,廣泛應用于激光雷達、相干光通信、遙感、工業(yè)超精密測量以及激光多普勒測振、測距和測速等眾多領域。然而,光外差探測實現(xiàn)條件非常苛刻,除了波前匹配、波矢匹配、模式匹配外,實際應用中,目標表面的粗糙特性也會嚴重影響回波外差探測效率。本文針對這一問題主要展開以下研究。1.對于光波來說,實際目標基本上都是粗糙的,目標表面粗糙程度的量化,對于定量分析粗糙目標對光外差探測的影響至關(guān)重要。通過蒙特卡羅方法,建立高斯型一維、二維隨機粗糙面模型,以高度起伏均方根代表粗糙表面的“縱向”變化,以相關(guān)長度代表粗糙表面的“橫向”變化,對實際粗糙目標表面形貌進行仿真,研究目標表面粗糙程度與這兩個參數(shù)之間的關(guān)系,為粗糙目標光外差性能理論分析奠定基礎。2.以蒙特卡羅方法建立的高斯隨機粗糙面模型作為目標,對光外差探測系統(tǒng)中信號光回波波前進行一維和二維仿真,對粗糙目標光外差探測中,信號光和本振光波前匹配惡化的現(xiàn)象進行說明。最后,使用波前分析儀,對光外差系統(tǒng)中光源波前、本振光波前、光滑目標信號光波前和粗糙目標信號光波前進行測量,實際測量結(jié)果與仿真結(jié)果一致,驗證信號光波前受粗糙目標表面調(diào)制,畸變嚴重。3.為了深入研究粗糙目標表面引起的“退相干”效應,通過蒙特卡羅方法建立的高斯隨機粗糙面目標,對目標回波信號的探測過程進行仿真,研究目標表面粗糙對中頻信號的影響,給出歸一化中頻電流在探測器光敏面上的一維和二維分布。此外,設計了粗糙面和光滑面兩組光外差探測實驗,驗證目標粗糙對中頻電流嚴重的“退相干”效應。實驗結(jié)果充分說明了理論分析結(jié)論。4.由于不同目標,表面粗糙程度不同,對信號光波前的調(diào)制效應也不同,實際的“退相干”效應也不同。針對這一問題,通過粗糙面的蒙特卡羅模型,研究了目標回波光外差信號與目標粗糙程度參數(shù)——均方根高度及相關(guān)長度的相互關(guān)聯(lián)。通過對大量不同粗糙程度目標光外差信號的數(shù)值仿真,給出了光外差信號與均方根高度及相關(guān)長度的定量關(guān)系曲線。最后,使用粗糙度比較樣塊作為目標,設計光外差實驗,驗證了仿真曲線。5.粗糙目標表面凹凸不平導致光外差信號隨機起伏,如何準確設置探測閾值,正確判決是否存在信號成為難題。傳統(tǒng)目標回波光外差探測使用高斯分布等簡單模型來描述,這常常導致判決誤差。提出一種準確獲得光外差信號概率密度曲線的方法,利用多項式對實際目標測量數(shù)據(jù)進行擬合,給出較準確的概率分布曲線。通過對某裝甲車表面樣塊多組測量數(shù)據(jù)的統(tǒng)計分析顯示,利用多項式擬合來確定判決閾值,比起用簡單的高斯分布來確定閾值,可以獲得更高的檢測概率和更低的誤警概率。研究表明:對實測中頻信號的統(tǒng)計直方圖進行多項式擬合的方法,有利于精確設置探測閾值,可以使檢測概率提高6.02%,誤警概率降低7.7%。6.目標振動特性是目標識別和激光雷達探測系統(tǒng)設計的關(guān)鍵技術(shù),也是光外差探測技術(shù)的一個重要應用。在理論分析目標振動特性測量原理的基礎上,設計了一套激光多普勒振動特性測量系統(tǒng),并且成功應用于實驗室內(nèi)音箱振動測量和室外汽車振動特性測量,得到相應的振動譜,這套系統(tǒng)也可以應用于其他振動目標(如飛機、坦克、艦船等)特性的測量,對精確打擊軍事目標和精確制導有重要意義,為激光多普勒探測的實用和推廣奠定了基礎。本文工作深入分析了粗糙目標光外差探測技術(shù)及其實際應用。研究了目標表面粗糙程度對光外差探測信號的影響,給出不同粗糙程度目標導致的退相干效應變化曲線,并設計實驗驗證了理論分析結(jié)果。還提出了一種提高探測閾值精度的方法,以裝甲車實測中頻信號進行說明,證明這種方法可以有效提高檢測概率。此外,在外場環(huán)境下,使用光外差探測技術(shù)成功測量了汽車振動譜。文中所取得的階段性成果為系統(tǒng)設計提供定量參考,也為探測系統(tǒng)性能評估仿真提供依據(jù)。
[Abstract]:Optical heterodyne detection is widely used in laser radar, coherent optical communication, remote sensing and industrial ultra-precision measurement because it can detect the amplitude, frequency and phase of the echo signal. In addition to wavefront matching, wavefront vector matching and pattern matching, the roughness of the target surface will also seriously affect the efficiency of echo heterodyne detection in practical applications. This paper focuses on this problem. 1. For light In terms of wave, the actual target is roughness basically, and the quantification of the roughness of the target surface is very important to quantitatively analyze the influence of the rough target on optical heterodyne detection. The length represents the "transverse" change of the rough surface. The surface topography of the actual rough target is simulated. The relationship between the roughness of the target surface and the two parameters is studied, which lays a foundation for the theoretical analysis of optical heterodyne performance of the rough target. 2. The Gaussian random rough surface model established by Monte Carlo method is used as the target to detect optical heterodyne. One-dimensional and two-dimensional simulation of signal light echo forward in the measurement system is carried out to illustrate the worsening matching between signal light and local oscillator in optical heterodyne detection of rough targets.Finally, the wavefront analyzer is used to analyze the light source wavefront, local oscillator wavefront, smooth target signal wavefront and rough target signal wavefront in optical heterodyne system. Measurements show that the wavefront of the signal is modulated by the rough surface of the target, and the distortion is serious. 3. In order to study the decoherence effect caused by the rough surface of the target, the detection process of the target echo signal is simulated by Monte Carlo method. The influence of surface roughness on IF signal is given, and the one-dimensional and two-dimensional distribution of normalized IF current on the photosensitive surface of the detector is given. In addition, two groups of optical heterodyne detection experiments are designed to verify the serious "decoherence" effect of target roughness on IF current. The experimental results fully illustrate the theoretical analysis conclusion. In order to solve this problem, the correlation between the optical heterodyne signal of target echo and the roughness parameter of target, the height of root mean square and the correlation length, is studied by Monte Carlo model of rough surface. The quantitative relationship curves between optical heterodyne signal and root mean square height and relative length are given by numerical simulation of a large number of optical heterodyne signals of different roughness degree targets.Finally, the optical heterodyne experiment is designed with the roughness comparison sample as the target to verify the simulation curves.5. The rough surface of the target causes random fluctuation of optical heterodyne signal. How to set the detection threshold accurately and decide whether there is a signal is difficult. Traditional target echo optical heterodyne detection is described by simple models such as Gaussian distribution, which often leads to decision error. A method to obtain the probability density curve of optical heterodyne signal accurately is proposed. The actual target measurement data is simulated by polynomial. Through the statistical analysis of several groups of measured data of an armored vehicle surface sample, it is shown that the decision threshold can be determined by polynomial fitting, and higher detection probability and lower false alarm probability can be obtained than by using simple Gaussian distribution to determine the threshold. Statistical histogram polynomial fitting method is advantageous to setting detection threshold accurately, which can increase detection probability by 6.02% and reduce false alarm probability by 7.7%. 6. Target vibration characteristic is the key technology of target recognition and lidar detection system design, and is also an important application of optical heterodyne detection technology. On the basis of the principle of property measurement, a laser Doppler vibration characteristic measurement system is designed and successfully applied to the vibration measurement of the loudspeaker in the laboratory and the vehicle in the outdoor. The corresponding vibration spectrum is obtained. This system can also be applied to the measurement of the characteristics of other vibration targets (such as aircraft, tanks, ships, etc.) to hit accurately. Attacking military targets and precise guidance is of great significance, which lays a foundation for the application and popularization of laser Doppler detection. In this paper, the optical heterodyne detection technology for rough targets and its practical application are deeply analyzed. The influence of the roughness of the target surface on the optical heterodyne detection signal is studied, and the decoherence caused by the targets with different roughness is given. A method to improve the accuracy of detection threshold is also proposed, which is illustrated by the measured IF signals of armored vehicles. It is proved that this method can effectively improve the detection probability. The phased results provide a quantitative reference for the design of the system and a basis for the performance evaluation and Simulation of the detection system.
【學位授予單位】：西安電子科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TN24
本文編號：2175613
[Abstract]:Optical heterodyne detection is widely used in laser radar, coherent optical communication, remote sensing and industrial ultra-precision measurement because it can detect the amplitude, frequency and phase of the echo signal. In addition to wavefront matching, wavefront vector matching and pattern matching, the roughness of the target surface will also seriously affect the efficiency of echo heterodyne detection in practical applications. This paper focuses on this problem. 1. For light In terms of wave, the actual target is roughness basically, and the quantification of the roughness of the target surface is very important to quantitatively analyze the influence of the rough target on optical heterodyne detection. The length represents the "transverse" change of the rough surface. The surface topography of the actual rough target is simulated. The relationship between the roughness of the target surface and the two parameters is studied, which lays a foundation for the theoretical analysis of optical heterodyne performance of the rough target. 2. The Gaussian random rough surface model established by Monte Carlo method is used as the target to detect optical heterodyne. One-dimensional and two-dimensional simulation of signal light echo forward in the measurement system is carried out to illustrate the worsening matching between signal light and local oscillator in optical heterodyne detection of rough targets.Finally, the wavefront analyzer is used to analyze the light source wavefront, local oscillator wavefront, smooth target signal wavefront and rough target signal wavefront in optical heterodyne system. Measurements show that the wavefront of the signal is modulated by the rough surface of the target, and the distortion is serious. 3. In order to study the decoherence effect caused by the rough surface of the target, the detection process of the target echo signal is simulated by Monte Carlo method. The influence of surface roughness on IF signal is given, and the one-dimensional and two-dimensional distribution of normalized IF current on the photosensitive surface of the detector is given. In addition, two groups of optical heterodyne detection experiments are designed to verify the serious "decoherence" effect of target roughness on IF current. The experimental results fully illustrate the theoretical analysis conclusion. In order to solve this problem, the correlation between the optical heterodyne signal of target echo and the roughness parameter of target, the height of root mean square and the correlation length, is studied by Monte Carlo model of rough surface. The quantitative relationship curves between optical heterodyne signal and root mean square height and relative length are given by numerical simulation of a large number of optical heterodyne signals of different roughness degree targets.Finally, the optical heterodyne experiment is designed with the roughness comparison sample as the target to verify the simulation curves.5. The rough surface of the target causes random fluctuation of optical heterodyne signal. How to set the detection threshold accurately and decide whether there is a signal is difficult. Traditional target echo optical heterodyne detection is described by simple models such as Gaussian distribution, which often leads to decision error. A method to obtain the probability density curve of optical heterodyne signal accurately is proposed. The actual target measurement data is simulated by polynomial. Through the statistical analysis of several groups of measured data of an armored vehicle surface sample, it is shown that the decision threshold can be determined by polynomial fitting, and higher detection probability and lower false alarm probability can be obtained than by using simple Gaussian distribution to determine the threshold. Statistical histogram polynomial fitting method is advantageous to setting detection threshold accurately, which can increase detection probability by 6.02% and reduce false alarm probability by 7.7%. 6. Target vibration characteristic is the key technology of target recognition and lidar detection system design, and is also an important application of optical heterodyne detection technology. On the basis of the principle of property measurement, a laser Doppler vibration characteristic measurement system is designed and successfully applied to the vibration measurement of the loudspeaker in the laboratory and the vehicle in the outdoor. The corresponding vibration spectrum is obtained. This system can also be applied to the measurement of the characteristics of other vibration targets (such as aircraft, tanks, ships, etc.) to hit accurately. Attacking military targets and precise guidance is of great significance, which lays a foundation for the application and popularization of laser Doppler detection. In this paper, the optical heterodyne detection technology for rough targets and its practical application are deeply analyzed. The influence of the roughness of the target surface on the optical heterodyne detection signal is studied, and the decoherence caused by the targets with different roughness is given. A method to improve the accuracy of detection threshold is also proposed, which is illustrated by the measured IF signals of armored vehicles. It is proved that this method can effectively improve the detection probability. The phased results provide a quantitative reference for the design of the system and a basis for the performance evaluation and Simulation of the detection system.
【學位授予單位】：西安電子科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TN24
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