【作者】 王焕钦；

【导师】 明海； 赵天鹏；

【作者基本信息】 中国科学技术大学 ， 微电子学与固体电子学， 2009， 博士

【摘要】 本论文工作是以中国科大物理系与美国微软公司西雅图硬件部的国际合作为背景,着重针对一维单模垂直腔面发射激光器(VCSEL)自混合测距、二维光学双镜头三角法测距和基于LED阵列飞行时间(Time of Flight:TOF)测距的三维成像三方面进行了深入的理论和实验研究。本文重点研究了影响单模VCSEL自混合测距的精度和动态范围等重要参数的各种因素,并对系统进行了优化设计;重点研究了二维光学双镜头三角法测距系统的光电设计方法,深入分析了光学双镜头三角法测距误差来源并对其进行了合理地修正;从原理结构和方法上提出一种新的基于LED阵列TOF测距的三维成像技术,深入地分析了实验结果,从理论上提出了简化的信噪比(Signal NoiseRatio:SNR)模型,合理的解释了深度图象像素数量、深度测量分辨率和深度测量速度等重要参数之间的制约关系,并且为系统优化设计提供了参考。本论文的主要研究工作和成果如下:1.完成了单模VCSEL自混合测距的原理与系统研究;设计了系统的光学和信号处理电路,搭建了单模VCSEL自混合测距系统原型样机;从理论和实验上对影响系统测距精度和动态范围等重要参数的各种因素进行了深入分析研究。应用差频模拟锁相技术代替快速傅立叶信号处理技术,选取最佳的三角波调制频率以及对单模VCSEL进行小电流调制等优化设计方法,可明显提高拍频信号信噪比,使测距精度达到2mm,动态范围扩大到50～500mm。2.完成了二维光学双镜头三角法测距的原理与系统研究;详细阐述了二维双镜头三角法测距系统的光学和电子学设计,研制了实时二维双镜头三角法测距系统样机,深入分析了系统测距误差来源并对其进行了修正。通过应用小孔成像代替普通镜头成像,从实验角度证明了大视角非近轴光线的镜头失真是造成测距误差的主要原因。基于实验的角度提出了一种经验修正公式,简化了理论修正公式的形式,明显地提高系统的测距精度和速度。修正后的测距系统实际工作范围可达80mm×100mm,分辨率高于0.2mm,定位精度优于2mm。3.从原理结构和方法上提出一种新的基于LED阵列TOF测距的三维成像技术。详细阐述了10×10的LED阵列TOF测距的三维成像系统的光学和电子学设计,构建了实时的10×10 LED阵列TOF测距的三维成像系统样机。深入地分析了TOF测距的结果,从理论上提出了简化的SNR模型,合理的解释了深度图象像素数量、深度测量分辨率和深度测量速度等重要参数之间的制约关系,并且为系统优化设计提供了参考。优化后的10×10 LED阵列TOF测距的三维成像系统在5～100cm的范围内,深度分辨率优于±5mm,图像获取速度可达10fps。本论文的创新点主要包括:1.利用差频模拟锁相技术处理VCSEL自混合信号,明显改善了自混合拍频信号在拐点处的不连续,同时对信号波形的调幅干扰和波形失真有明显抑制效果,明显提高拍频信号的信噪比,提高了测距精度和动态范围。对单模VCSEL选取合适的三角波调制频率以及进行小电流调制等优化设计方法,可以改善自混合拍频信号频率的测量精度和减小由激光器非线性调制引入的测距误差。2.从实验角度证明了光学双镜头三角法测距系统中大视角非近轴光线的镜头失真是造成测距误差的主要原因,并与基于镜头大视角成像的高阶畸变理论分析的结果一致。针对复杂理论修正公式,基于实验的角度提出了一种经验修正公式,简化了修正公式的形式,明显地提高系统的测距精度和速度。3.从原理结构和方法上提出一种新的基于LED阵列TOF测距的三维成像技术。应用快速时分扫描光功率调制的LED阵列方法实现了无需机械移动高速采样的深度测量;应用“共透镜”法实现了两维图象与深度图像的高精度对准。设计了新型的快速响应的FBAGC电路,提高了系统的测量速度。基于理论分析提出了简化的SNR模型,合理的解释了深度图象像素数量、深度测量分辨率和深度测量速度等重要参数之间的制约关系,并验证了构建实时高像素三维成像系统的可行性。更多还原

【Abstract】 The works in this dissertation are based on the international cooperation between Department of Physics,University of Science and Technology of China(USTC) and Seattle Hardware Division of Microsoft,which includes theoretical and experimental research on one-dimensional(1D) single mode vertical-cavity surface-emitting laser (VCSEL) range finding,two-dimensional(2D) triangulation-based optical rang finding with dual lens and three-dimensional(3D) imaging based on LED array time of flight(TOF) range finding.We have put emphasis on the study of various factors which influence the range accuracy and dynamic range of laser range finder,and emphasized the study of the photoelectric design method for 2D triangulation-based optical rang finder with dual lens,and give in-depth analysis and appropriate remedy on the triangulation ranging error.Also we have proposed a new 3D imaging system based on LED array time of flight(TOF) range finder,analyzed the experimental results in detail and developed a simple Signal Noise Ratio(SNR) model to explain the mutual restriction among the pixel number of depth image,depth measurement resolution and depth measurement speed,which give a good guidance for the optimized design of the 3D imaging system.The main research works and conclusions are as follows:1.We accomplished the theory and system researches of laser range finding by self-mixing effect in a single mode VCSEL,designed the optics and signal processing circuit for the system and builded the protype of the single mode VCSEL laser range finder;We analyzed various factors influencing the system key parameters in theory and experiment,such as ranging accuracy and dynamic range,etc.By applying difference frequency analog phase-locked loop(PLL) instead of Fast Fourier Transform(FFT) to process self-mixing beat signal,choosing the optimum triangular wave frequency and small current to modulate single-mode VCSEL,the signal noise ratio(SNR) of beat signal has been enhanced,which finally makes the ranging accuracy is better than 2 mm and the measurement dynamic range is as large as 50～500 mm. 2.We completed the theory and system researches of the 2D triangulation-based optical rang finding with dual lens,delivered the optics and electronics design for this system in detail,constructed the protype of real-time 2D triangulation-based optical rang finder and gave in-depth analysis and appropriate remedy on the triangulation ranging error.By applying the pinhole imaging instead of normal lens imaging to study 2D ranging,we demonstrated the large visual angle abaxial light aberration of lens is the main reason for the ranging error,and propose an empirical remedy equation based on experiments,which not only simplify the form of theoretical remedy equation but also obviously improve ranging accuracy and speed.The actual work region of this ranging system after remedy is as large as 80 mm×100 mm,the average resolution and ranging error in x and y direction are better than 0.2 mm and 2 mm,respectively.3.We proposed a new 3D imaging system based on LED array time of flight range finder in principle and structure,gave the detail design on the optics and electronics for the 10×10 LED array 3D imaging system,and builded the real time protype.Moreover,we analyzed the experimental results in detail and developed a simple SNR model to explain the mutual restriction among the pixel number of depth image,depth measurement resolution and depth measurement speed,which gives a good guidance for the optimized design of the 3D imaging system.The 10×10 LED array 3D imaging system after optimization can acquire at a rate of 10 frames per second(fps) with a depth resolution better than±5mm in the range of 5～100 cm.The innovative results in this dissertation are as follows:1.Use difference frequency analog PLL to process self-mixing beat signal,so the phase abrupt changes in the beat signal corresponding to the inflection points of the modulation triangular waves have been improved obviously,and the amplitude modulation and distorted waveform has been rejected obviously, which enhance the SNR of beat signal and finally improve,the ranging accuracy and measurement dynamic range.By choosing the optimum triangular wave frequency and small current to modulate single-mode VCSEL, the frequency measurement accuracy of self-mixing beat signal be improved and the ranging error introduced by VCSEL nonlinear modulation can be reduced.2.Based on experiment,we demonstrated the large visual angle abaxial light aberration of lens is the main reason for the ranging error in the 2D triangulation-based optical rang finder with dual lens,which keeps good agreement with the high order distortion theory of imaging lens.We also proposed an experiment-based empirical remedy equation,which not only simplify the form of theoretical remedy equation but also obviously improve ranging accuracy and speed.3.We proposed a new 3D imaging system based on LED array time of flight range finder in principle and structure.The high speed depth measurement can be achieved by employs fast electronic time-division scanning of a two-dimensional array of LED light sources instead of using mechanical scanning,which means no moving or rotating parts are needed in this system. The co-lens method is used to assure the natural registration between the range image and 2D image.The design of fast feedback AGC(FBAGC) circuit obviously reduces the system feedback response time and improves system measurement speed.Based on the theoretical analysis,a simple SNR model is developed to explain the mutual restriction among the pixel number of depth image,depth measurement resolution and depth measurement speed.Finally, the feasibility of implementing a real time large pixels version of the system is also demonstrated.更多还原