粗糙目標(biāo)對(duì)光外差探測(cè)信號(hào)的退相干效應(yīng)
發(fā)布時(shí)間：2018-08-10 17:11
【摘要】：光外差探測(cè)是公認(rèn)的具有量子探測(cè)極限本領(lǐng)的相干探測(cè)體制,可以實(shí)現(xiàn)對(duì)回波信號(hào)振幅、頻率和相位攜帶信息的全息探測(cè),在微弱信號(hào)探測(cè)方面,具有直接探測(cè)不可比擬的優(yōu)點(diǎn),廣泛應(yīng)用于激光雷達(dá)、相干光通信、遙感、工業(yè)超精密測(cè)量以及激光多普勒測(cè)振、測(cè)距和測(cè)速等眾多領(lǐng)域。然而,光外差探測(cè)實(shí)現(xiàn)條件非�？量�,除了波前匹配、波矢匹配、模式匹配外,實(shí)際應(yīng)用中,目標(biāo)表面的粗糙特性也會(huì)嚴(yán)重影響回波外差探測(cè)效率。本文針對(duì)這一問(wèn)題主要展開(kāi)以下研究。1.對(duì)于光波來(lái)說(shuō),實(shí)際目標(biāo)基本上都是粗糙的,目標(biāo)表面粗糙程度的量化,對(duì)于定量分析粗糙目標(biāo)對(duì)光外差探測(cè)的影響至關(guān)重要。通過(guò)蒙特卡羅方法,建立高斯型一維、二維隨機(jī)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(zhǎng)度代表粗糙表面的“橫向”變化,對(duì)實(shí)際粗糙目標(biāo)表面形貌進(jìn)行仿真,研究目標(biāo)表面粗糙程度與這兩個(gè)參數(shù)之間的關(guān)系,為粗糙目標(biāo)光外差性能理論分析奠定基礎(chǔ)。2.以蒙特卡羅方法建立的高斯隨機(jī)粗糙面模型作為目標(biāo),對(duì)光外差探測(cè)系統(tǒng)中信號(hào)光回波波前進(jìn)行一維和二維仿真,對(duì)粗糙目標(biāo)光外差探測(cè)中,信號(hào)光和本振光波前匹配惡化的現(xiàn)象進(jìn)行說(shuō)明。最后,使用波前分析儀,對(duì)光外差系統(tǒng)中光源波前、本振光波前、光滑目標(biāo)信號(hào)光波前和粗糙目標(biāo)信號(hào)光波前進(jìn)行測(cè)量,實(shí)際測(cè)量結(jié)果與仿真結(jié)果一致,驗(yàn)證信號(hào)光波前受粗糙目標(biāo)表面調(diào)制,畸變嚴(yán)重。3.為了深入研究粗糙目標(biāo)表面引起的“退相干”效應(yīng),通過(guò)蒙特卡羅方法建立的高斯隨機(jī)粗糙面目標(biāo),對(duì)目標(biāo)回波信號(hào)的探測(cè)過(guò)程進(jìn)行仿真,研究目標(biāo)表面粗糙對(duì)中頻信號(hào)的影響,給出歸一化中頻電流在探測(cè)器光敏面上的一維和二維分布。此外,設(shè)計(jì)了粗糙面和光滑面兩組光外差探測(cè)實(shí)驗(yàn),驗(yàn)證目標(biāo)粗糙對(duì)中頻電流嚴(yán)重的“退相干”效應(yīng)。實(shí)驗(yàn)結(jié)果充分說(shuō)明了理論分析結(jié)論。4.由于不同目標(biāo),表面粗糙程度不同,對(duì)信號(hào)光波前的調(diào)制效應(yīng)也不同,實(shí)際的“退相干”效應(yīng)也不同。針對(duì)這一問(wèn)題,通過(guò)粗糙面的蒙特卡羅模型,研究了目標(biāo)回波光外差信號(hào)與目標(biāo)粗糙程度參數(shù)——均方根高度及相關(guān)長(zhǎng)度的相互關(guān)聯(lián)。通過(guò)對(duì)大量不同粗糙程度目標(biāo)光外差信號(hào)的數(shù)值仿真,給出了光外差信號(hào)與均方根高度及相關(guān)長(zhǎng)度的定量關(guān)系曲線。最后,使用粗糙度比較樣塊作為目標(biāo),設(shè)計(jì)光外差實(shí)驗(yàn),驗(yàn)證了仿真曲線。5.粗糙目標(biāo)表面凹凸不平導(dǎo)致光外差信號(hào)隨機(jī)起伏,如何準(zhǔn)確設(shè)置探測(cè)閾值,正確判決是否存在信號(hào)成為難題。傳統(tǒng)目標(biāo)回波光外差探測(cè)使用高斯分布等簡(jiǎn)單模型來(lái)描述,這常常導(dǎo)致判決誤差。提出一種準(zhǔn)確獲得光外差信號(hào)概率密度曲線的方法,利用多項(xiàng)式對(duì)實(shí)際目標(biāo)測(cè)量數(shù)據(jù)進(jìn)行擬合,給出較準(zhǔn)確的概率分布曲線。通過(guò)對(duì)某裝甲車(chē)表面樣塊多組測(cè)量數(shù)據(jù)的統(tǒng)計(jì)分析顯示,利用多項(xiàng)式擬合來(lái)確定判決閾值,比起用簡(jiǎn)單的高斯分布來(lái)確定閾值,可以獲得更高的檢測(cè)概率和更低的誤警概率。研究表明:對(duì)實(shí)測(cè)中頻信號(hào)的統(tǒng)計(jì)直方圖進(jìn)行多項(xiàng)式擬合的方法,有利于精確設(shè)置探測(cè)閾值,可以使檢測(cè)概率提高6.02%,誤警概率降低7.7%。6.目標(biāo)振動(dòng)特性是目標(biāo)識(shí)別和激光雷達(dá)探測(cè)系統(tǒng)設(shè)計(jì)的關(guān)鍵技術(shù),也是光外差探測(cè)技術(shù)的一個(gè)重要應(yīng)用。在理論分析目標(biāo)振動(dòng)特性測(cè)量原理的基礎(chǔ)上,設(shè)計(jì)了一套激光多普勒振動(dòng)特性測(cè)量系統(tǒng),并且成功應(yīng)用于實(shí)驗(yàn)室內(nèi)音箱振動(dòng)測(cè)量和室外汽車(chē)振動(dòng)特性測(cè)量,得到相應(yīng)的振動(dòng)譜,這套系統(tǒng)也可以應(yīng)用于其他振動(dòng)目標(biāo)(如飛機(jī)、坦克、艦船等)特性的測(cè)量,對(duì)精確打擊軍事目標(biāo)和精確制導(dǎo)有重要意義,為激光多普勒探測(cè)的實(shí)用和推廣奠定了基礎(chǔ)。本文工作深入分析了粗糙目標(biāo)光外差探測(cè)技術(shù)及其實(shí)際應(yīng)用。研究了目標(biāo)表面粗糙程度對(duì)光外差探測(cè)信號(hào)的影響,給出不同粗糙程度目標(biāo)導(dǎo)致的退相干效應(yīng)變化曲線,并設(shè)計(jì)實(shí)驗(yàn)驗(yàn)證了理論分析結(jié)果。還提出了一種提高探測(cè)閾值精度的方法,以裝甲車(chē)實(shí)測(cè)中頻信號(hào)進(jìn)行說(shuō)明,證明這種方法可以有效提高檢測(cè)概率。此外,在外場(chǎng)環(huán)境下,使用光外差探測(cè)技術(shù)成功測(cè)量了汽車(chē)振動(dòng)譜。文中所取得的階段性成果為系統(tǒng)設(shè)計(jì)提供定量參考,也為探測(cè)系統(tǒng)性能評(píng)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(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TN24
本文編號(hào)：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(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TN24
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