本文選題：激光雷達(dá) + 調(diào)頻連續(xù)波�。� 參考：《哈爾濱工業(yè)大學(xué)》2014年碩士論文

【摘要】：調(diào)頻連續(xù)波（FMCW）激光雷達(dá)具有高精度、高效率、非接觸無(wú)需靶標(biāo)、大尺寸無(wú)盲區(qū)等優(yōu)點(diǎn)，能夠在多種場(chǎng)合工作，是測(cè)量近距離大尺寸目標(biāo)的重要方法之一。本文通過(guò)對(duì)FMCW激光雷達(dá)中的關(guān)鍵技術(shù)要點(diǎn)的研究，建立了線性調(diào)頻連續(xù)波激光雷達(dá)測(cè)距系統(tǒng)，對(duì)系統(tǒng)信號(hào)進(jìn)行了分析與處理，來(lái)提高絕對(duì)距離測(cè)量的精度，，根據(jù)系統(tǒng)要求，對(duì)關(guān)鍵器件進(jìn)行了選取，搭建了實(shí)驗(yàn)平臺(tái)。 FMCW絕對(duì)距離測(cè)量是依賴于激光器線性調(diào)頻的，而實(shí)際中激光器頻率調(diào)諧很難做到嚴(yán)格線性，這會(huì)引起差拍干涉頻率展寬，從而引入較大的測(cè)量誤差，本文根據(jù)FMCW測(cè)距技術(shù)的基本原理，研究了基于頻率采樣的方法來(lái)校正激光調(diào)諧非線性，采用馬赫澤德干涉儀作為校正時(shí)鐘，對(duì)原測(cè)量信號(hào)進(jìn)行外部時(shí)鐘采樣，由于校正信號(hào)路和測(cè)量信號(hào)路含有相同的非線性，通過(guò)同步采樣消除了非線性成分。由于系統(tǒng)采用全光纖器件設(shè)計(jì)，不同頻率的激光在光纖中走過(guò)的光程也不一樣，而測(cè)量路在自由空間中的光程隨頻率的變化可以忽略，測(cè)量路與校正路的色散量不能抵消，帶來(lái)色散誤差，本文對(duì)系統(tǒng)中可能存在的色散問(wèn)題進(jìn)行了分析論證，并且通過(guò)建模對(duì)色散誤差進(jìn)行了仿真模擬。FMCW技術(shù)的本質(zhì)是干涉測(cè)量，實(shí)際中由于光纖的彎曲、應(yīng)力變化或者環(huán)境影響都有可能導(dǎo)致參與干涉的測(cè)量臂和參考臂的兩束光的偏振態(tài)發(fā)生改變，引起干涉信號(hào)的幅度衰落，甚至衰落為零，干涉現(xiàn)象完全消失，本文對(duì)這種偏振衰落問(wèn)題對(duì)FMCW的影響進(jìn)行了分析。在外部時(shí)鐘采樣中，由于校正信號(hào)路光學(xué)頻率間隔的變化以及在AD采樣或者校正信號(hào)到時(shí)鐘信號(hào)的轉(zhuǎn)換過(guò)程中引入的采樣時(shí)延會(huì)導(dǎo)致外部時(shí)鐘產(chǎn)生誤差，從而導(dǎo)致采樣誤差。本文對(duì)采樣誤差以及采樣誤差引起的色散進(jìn)行了分析討論。 基于FMCW理論，選取1550nm波段連續(xù)可調(diào)諧外腔式激光器作為光源，采用全光纖器件搭建光路，利用平衡探測(cè)器探測(cè)差拍信號(hào)，最后用高速采集卡獲取數(shù)據(jù)。編寫了Labview測(cè)量軟件，對(duì)光纖端面以及自由空間中的量塊進(jìn)行測(cè)距實(shí)驗(yàn)，并且使用高精度導(dǎo)軌和雙頻激光干涉儀對(duì)測(cè)距結(jié)果進(jìn)行標(biāo)定，實(shí)驗(yàn)結(jié)果表明基于頻率采樣的方法很好的校正了激光器掃頻的非線性，測(cè)距穩(wěn)定性很高，但是光纖色散以及采樣誤差對(duì)測(cè)距精度的影響較大，只有通過(guò)對(duì)色散和采樣誤差進(jìn)行算法或者光路延遲補(bǔ)償才能獲得更高的精度。
[Abstract]:FM CW FMCW laser radar has the advantages of high precision, high efficiency, no target in contact, no blind area in large size and so on. It is one of the important methods for measuring large and short range targets. Based on the study of the key technical points in FMCW lidar, a linear frequency modulation continuous wave laser radar ranging system is established in this paper. The signal of the system is analyzed and processed to improve the accuracy of absolute range measurement, according to the requirements of the system. The key devices are selected and the experimental platform is built. The absolute distance measurement of FMCW depends on the linear frequency modulation of the laser, but the frequency tuning of the laser is difficult to achieve strict linearity in practice, which will lead to the broadening of the beat interference frequency. According to the basic principle of FMCW ranging technology, the method based on frequency sampling to correct the laser tuning nonlinearity is studied in this paper. The Mahezard interferometer is used as the correction clock. For the external clock sampling of the original measurement signal, the nonlinear component is eliminated by synchronous sampling because the correction signal circuit and the measurement signal circuit contain the same nonlinearity. Because the system is designed with all optical fiber devices, the optical path of laser with different frequencies is different in the optical fiber, and the change of the optical path of the measurement path in free space with the frequency can be ignored, and the dispersion between the measuring path and the correction path cannot be offset. This paper analyzes and demonstrates the possible dispersion problem in the system, and simulates the dispersion error by modeling. The essence of the dispersion error is interference measurement. In practice, because of the bending of optical fiber, The change of stress or environmental influence may lead to the change of the polarization state of the two beams of light involved in the interferometer and the reference arm, which will cause the amplitude fading of the interference signal, or even decline to zero, and the interference phenomenon will disappear completely. The influence of this polarization fading problem on FMCW is analyzed in this paper. In the external clock sampling, because of the change of the optical frequency interval of the correction signal path and the sampling delay introduced in the AD sampling or the conversion process of the correction signal to the clock signal, the external clock will produce errors, which will lead to the sampling error. In this paper, the sampling error and the dispersion caused by the sampling error are analyzed and discussed. Based on the theory of FMCW, the continuous tunable external cavity laser in 1550nm band is selected as the light source, and all optical fiber devices are used to build the optical circuit. The balance detector is used to detect the beat signal, and the high speed data acquisition card is used to obtain the data. LabVIEW measurement software is developed to measure the optical fiber end surface and the measuring block in free space. The distance measurement results are calibrated by using high precision guideway and dual-frequency laser interferometer. The experimental results show that the method based on frequency sampling corrects the nonlinearity of laser frequency sweep and has high ranging stability, but fiber dispersion and sampling error have great influence on ranging accuracy. A higher precision can be obtained only through the algorithm of dispersion and sampling error or the compensation of optical path delay.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN957.51

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