【作者】 刘金凤；

【导师】 贺顺忠；

【作者基本信息】 天津大学 ， 光学工程， 2004， 硕士

【摘要】 为了勘探石油、天然气等矿藏及地热、水文地质、工程地质等地下资源和信息,人们开发研究各种勘探方法,其中地震勘探方法是发展历史最长,技术最成熟,应用最广,最有效的一种勘探方法。传统的地震检波器由于检测精度不够大、灵敏度不够高、易受电磁干扰等缺点,已经不能满足日益发展的地震勘探的要求。而激光多普勒测量方法由于具有精度高、频带宽、动态响应快、线性度好、测量范围大、非接触测量等优点,应用和发展很快。本文研究了激光多普勒测振技术,提出用激光多普勒参考光检波系统来测量地震波所引起的振动,并对其进行了原理性实验。主要完成了以下工作: 1.根据多普勒效应测振技术的理论分析,设计了激光多普勒参考光检波光路,实现了激光频移和光路的外差。2.在谐振腔中插入光阑得到了基横模激光输出,并采用倒置的望远镜对激光进行扩束准直,提高了激光的方向性,改善了光斑质量,提高了信号质量。3.引入特伦逆向反射系统对光路进行优化,分析了其多普勒频移与物体振动速度之间的关系,提高了光学测量系统的测量精度和抗偏摆、横移的能力。4.研究声光调制器的调制原理,通过实验确定了二氧化碲声光调制器衍射光与入射光偏振态之间的关系,并通过在光路中插入1/4波片使测量光与参考光的偏振态达到匹配,提高了信号强度和信噪比。5.研究锁相环电路原理,用NE568A单片锁相环来解调调频信号。6.完成了对整个系统的调试,数据的记录及实验数据的分析。实验证明系统的测量精度可达1%。更多还原

【Abstract】 To detect mineral resources and other information underground, many detection methods have been researched and developed, in which the method of seismic prospecting is one of the most effective methods. It has been applied widespreadly and the technology about it has developed rapidly. However, on one hand seismic detector is important tool of seismic prospecting. Traditional seismic detectors have not satisfied the requirement of seismic prospecting developing increasingly due to low measurement accuracy, low response and sensitive to electromagnetic interference. On the other hand, because of high accuracy, wide band, quick dynamic response, good linearity, large measurement range and untouched measurement, laser Doppler measurement develops rapidly. In this paper, based on a new method of seismic prospecting, that is remoter measurement scheme to seismic wave, laser Doppler measurement of vibration is researched, and laser Doppler reference optic structure of demodulation system is put forward to measure the vibration caused by seismic waves, and the principle experiment is carried out. The following achievements are completed: 1. Theory of the measurement of vibration using Laser Doppler effect are researched and reference Laser Doppler optical system are designed. Especially, acousto-optic modulator is used in this system to implement laser heterodyne, which can improve the signals’ SNR and anti-jamming ability of the optical system. 2. According to theory of laser Doppler measurement, optical measurement system is optimized. Introducing Trent reversed reflection structure to improve measurement accuracy of optical system and the ability of anti-traversing and anti-beating. 3. PLL (phase locked loop) circuit is researched to detect and demodulate weak Doppler signals with monolithic PLL circuit NE568A. NI’s DAQ card is used to acquire data. The adjustment of the whole system, acquisition of data and analysis of experiment data are completed. In the end, the software labview is applied to get amplitude and frequency parameters of vibration.更多还原