文献翻译一--XXX.doc

外文原文（一）Laser ranging based on electro-optic switchDong Zhao, Liren Liu, Jiming Wang, Haitao Lang, Weiqing PanAbstract：Based on electro-optic switch effect in crystal, a novel laser ranging method is proposed. CW-laser emitted by laser transmitter propagates forward to the measured target, after being reflected by the target, and then goes back to the transmitter. Close to the transmitter, a special mono-block LiNbO3 crystal is added into the round-trip light beams. High-voltage pulses with the sharp enough changes in rising edges are loaded on the crystal. Based on electro-optic effect, double refraction and internal double reflection effect in crystal, the crystal cuts off the round-trip light beams,and reflects a light pulse cut out by the crystal to a detector aside from the original beam path. The pulse width T is the period that laser propagates forward and back between the crystal and the target. The feasibility of the new idea is proved by our experiments and a brand-new way for the laser ranging is provided.1. IntroductionBased on the Pockels effect (linear electro-optic effect) in crystal, when a laser travels through a crystal, by adjusting the electric-field loaded on the crystal, one can change the phasic difference of two linearly polarized components of the laser, which induces a variation in the polarization state of the laser, and then adjust the polarization state of the laser 1. In this paper, the preceding electro-optic characters are utilized in laser ranging region, where the loaded electro-field is modu-lated fast enough, and induces a fast modulation on the polarization state of the laser between the crystal and the measured target. And based on double refraction effect and internal double reflect ion effect in the anisotropic uniaxial crystal, the polarizer, polarization analyzer and electro-optic modulator can be integrated into a mono-block crystal with special shape. Therefore, the special crystal can be used to fulfill all the analysis and abstraction missions of the required range information in laser ranging .At present, there are several major methods in laser ranging region, such as the pulsed time-of-flight laser ranging based on laser pulse 2-4, the phase-shift method based on modulated laser phase5-7, the frequency comparison method based on modulated laser frequency8-10 , and the mixed methods of some ones of the above 11 . However, these preceding methods need some complex additional circuit systems to handle the range information. To author s knowledge, there are no ranging methods reported based on electro-optic switch effect and polarization effect in crystal. In this paper, a new ranging method based on electro-optic effect in crystal is proposed , which mostly handles and abstracts range information in optic region. And the device is simple and easy to be realized due to the use of the common LiNbO3 as a main part.2. Principle and structureThe original conception is shown in Fig. 1. The CW-laser from the transmitter propagates forward to the measured target, being reflected by the target, then goes back to the source. Now , supposing that a reflecting mirror is instantaneously inserted into the round -trip light beams at an angle of 45。, whose reflecting surface is toward the target. Both of the forward and backward laser beams would be shut off, and at the same time the backward beam is reflected downwards to a detector. Due to the insertion of the mirror, the segment of light beams between mirror and target is cut out and detected as a rectangular light pulse. The width T of the pulse is the period that laser propagates forward and back between the mirror and the target. The required range R can be obtained fromR =cT/2， （1）where c is the light velocity in air.Due to the fast responses to loaded voltages in crystals, the above function of inserting instantaneously the mirror can be realized based on the Pockels effect in uniaxial crystals. As shown in Fig. 2 , a mono-block LiNbO3 crystal with special shape is designed as the main part in this laser ranging system. The reference coordinates are x, y and z equaling to the crystallographic axis, and the electric inductive principle axes are x, y and z in Fig.2. A rectangular parallelepiped LiNbO3 crystal is cut with a slope angle of 45、, where the cut plane parallels x and intersects y and z at an angle of 45、.When the random polarized light from laser source enters the crystal under the 45、 oblique plane, the vertical incidence light beam is decomposed into two crossed linearly polarized components o light and e light, due to the cross-cut between wave vector and crystal axis C.The o and e propagate in the same direction. After crashing into the 45。 oblique plane, both of the o and e lights are reflected totally, because the incident angle of 45。 is larger than critical angle of about 28。. The double refraction and reflection of sequential interfaces in crystals have been studied detailedly in the earlier works of our laboratory12,13 .The studies show that the o light propagates along z axis and leaves vertically the crystal, and the e light propagates in the direction at an angle of about 2。 from z direction after being reflected, and leaves the crystal at an angle of about 5。 from z direction after being refracted at the interface. That is to say, there is an angle of about 5。 large enough to separate the exit e beam(useless) and o beam (useable).A pair of slender electrodes, which cover exactly they dimension of the o beam, are added along the forward o light on the two y z planes of the crystal. In the absence of applied electric-field, the forward o light is reflected by the target and travels back to the laser source along the same route. After loading some voltage on the electrodes, the electric inductive principle axes x and y rotate an angle of 45。 from initial axes x and y on z axis,due to the electric-field vector paralleling x axis. The electric inductive index ellipsoid of the EO crystal is expressed asThe principal refractive indexes of the new optical indicatrix areTherefore, after the o light traversing the electric-field, the phasic difference between the two linearly polarized components corresponding to x and y is expressed aswhere l is the electrode length in z direction ,d is the xextension of the crystal, is the laser wave length , V is the loaded voltage, n0 = 2.287 is intrinsic refractive index, and 22=3.4x10-12m/V is the corresponding component of the electro-optic tensors relating the electric-field in crystal. Making the value of Eq. (4) be , one can get a voltageThe voltage V is called the half-wave voltage, which mean s a phasic difference would be introduce d, if the V is loaded on crystals.Now, a half-wave voltage V is loaded rapidly enough on the crystal. On the one hand, the backward light beam reflected by the target is modulated instantaneously by the loaded electric-field, and converted from o light polarizing along x to e light polarizing along y .After being reflected totally at the 45。 oblique plane, the e light travels in the direction at an angle of about 2。 from y direction in the crystal, and leaves the crystal at an angle about 5。 from -y direction to the detector12,13 . The above jumping moment is detected as the front edge (rising edge) of the light pulse. On the other hand , at the same time the forward light beam from the source is instantaneously modulated too, and converted from o light polarizing a long x to e light polarizing Along y . The e light travels forward and is reflected by target. While returning to the crystal, the e light is modulated at the second time and converted to o light again. After crashing into the 45。 oblique plane, the o light polarizing along x is reflected to the laser source in y direction. The above jumping moment is detected as the back edge (falling edge) of the pulse. Thus, the detected light pulse is formed, which contains the information of measured range. Here the mono-block LiNbO3 fulfilled the task of analyzing and extracting the measured range R information.The available light paths in Fig.2 are laser source45。 oblique plane electrodestarget electrodes 45。oblique plane detector. To help to understand the functions of the crystal, making the target the center of symmetry, the mono-block crystal ranging system in Fig. 2 can be equivalent to the device in Fig. 3, after the useless portions deleted. The reference coordinates in Fig. 3 are same as one s in Fig. 2. Here the 45。oblique plane is equivalent to a polarizer when light travels from the source to the target, and a crossed polarization analyzer when light goes from the target to the source.译文（一）基于光电开关的激光测距董钊，刘利人，王启明，郎海涛，潘蔚青摘要：基于晶体光电开关效应，是一种新型的激光测距方法。激光发射器通过连续发送激光到被测目标，之后由被测目标反射回激光发射器。关闭发射器，将一个特殊的单块LiNbO3晶体加入这些往返光束。于是足够尖锐的高电压脉冲在上升沿时就被加载到晶体中。根据晶体中的双折射和内部双重折射的光电效应，晶体将切断往返光束，并且通过晶体检测出反射光脉冲的原光束路径。脉冲宽度T是激光往返于晶体与被测目标之间的周期。我们的实验和提供的激光测距的新方法证明了这个新想法的可行性。1.介绍基于晶体的波尔克斯效应（线性光电效应）是当激光穿过过晶体时，通过调节电场对晶体的加载，可以改变激光器的两个线性偏振分量的相位差，即诱导激光的偏振状态的变化，然后再调整激光的偏振状态。在本文中，前面所述的激光效应的特征被用在激光测距的领域。被加载的电场足够快的进行调制，并且在晶体和被测目标之间引发一个快速调制的激光偏振状态。由于在不同单块晶体之中存在双折射效应和内部离子的双重反射效应，偏振片，检偏器和光电调制器便可以被集成到具有特殊形状的单块晶体之中。因此，特殊的晶体可用于满足激光测距所需要信息的分析和提取任务。目前，在激光测距领域有几个主要的方法，例如基于激光脉冲的飞行时间激光脉冲测2-4 基于激光相位调制的相移方法5-7，基于激光频率调制的频率比较方法8-10，和上述方法的结合11 ，然而，上述所说的这些方法需要一些复杂的传统电路系统来实现。对于基于光电开关效应和晶体极化效应的知识本文不做详细的叙述。在本文中，报告了基于晶体中的光电效应的一个新的广泛使用的方法。该方法在光电领域范围内掌握和摘取了主要的一些信息。这个方法通过使用共同的LiNbO3做为主要的部分来实现，十分简单和容易。2.原理与结构原概念如图1所示，激光发射器朝着被测物体连续发送激光，然后由被测物体反射回激光发射器。现在，假设一个反射镜的反射面朝着被测目标以45度角瞬时插入到往返光束中。前后两个激光束会被切断，并在同一时间往回反射到检测器。由于反射器的插入，镜子与被测物体之间的光片段会被切断并且会以矩形光脉冲的形式被检测到。脉冲宽度T是激光往返在晶体与被测目标之间的周期。所求范围R可以从公式R =cT/2中得到，其中c是光在空气中的传播速度。图1 原概念图由于晶体加载电压时的快速反应，上述的瞬间插入反射镜的功能可以根据单轴晶体的波尔克斯效应来实现，如图2所示，具有特殊形状的单轴晶体LiNbO3被设计成该激光测距系统的主要部分。在图2中，参考坐标x,y,z分别表示晶轴，x,y,z分别表示电感准则轴。在一个矩形的平行六面体上切出一个45度的倾斜角，所切平面平行于x轴并且和y轴与z轴呈45度角相交。当激光源的偏振光从45度角的斜平面射入晶体中时，由于在波向量和晶轴C之间的横切，垂直入射的光束会被分解成两个相交的直线偏振光分量o和e，o和e在同一方向传播，又因为45度的入射角要大于28度的临界角，所以在经过45度角的倾斜面之后，o和e两个