共查询到20条相似文献,搜索用时 957 毫秒
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三维形貌测量中基于错位条纹的解相位方法 总被引:2,自引:1,他引:1
针对光栅投影法三维测量中的相位展开问题,提出一种用四步相移法求取折叠相位的解决方案.在相移图中,提取带有90°相移的4个单周期正弦条纹,对4个单周期正弦条纹进行编码组合,生成错位条纹.测量中,摄像机获取的错位条纹图像和相移图像按灰度值相减,得到4幅条纹差图,提取各差图中灰度值为零的条纹,依此确定错位条纹图像中各个单周期... 相似文献
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液晶光调制计算全息相移器 总被引:12,自引:3,他引:9
在同轴相移数字全息实验中,相移量的准确性、稳定性对实验结果起着很重要的作用,因此相移器的研究已成为相移数字全息实验研究中的一个重要内容。在以往应用的相移器中,大多是通过机械驱动改变光程来实现相移,这种方法会使光路变得复杂。提出了一种新型的相移器——液晶光调制计算全息相移器,它将大大简化光路的设计,同时避免机械运动,实现相移量的全数字化控制。该相移器是基于计算全息原理和傅里叶变换的位移定理所提出的,它将液晶显示器(LCD)作为光学显示元件,通过适当改变显示在液晶显示器上的计算全息图的编码,使其同时实现波面变换和相移。给出了液晶光调制计算全息相移器的理论分析,并通过实验测量表明其相移量的波动范围仅在0.036 rad以内,具有很高的精确性、可重复性和稳定性,最后验证了该相移器用于同轴相移数字全息实验的可行性。 相似文献
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偏振相移电子错位散斑干涉术及其应用于弯曲板的曲率测量 总被引:2,自引:0,他引:2
叙述偏振相移电子错位散斑干涉术的原理以及用可调阶数最小二乘多项式拟合斜度分布求导的方法。用于周边固支矩形板的曲率测量和理论计算结果符合很好。 相似文献
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在相移式轮廓测量(PMP)技术中,提出了一种基于查表法的相移校正算法,使传统的N步计算方法要以适用于任何相移值(非等步相移)的情况,从而降低了对相移器的精度要求。利用计算机传真技术验证了该修正算法的正确性。 相似文献
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详细介绍了一种由计算机控制的PZT相移器,该相移器由D/A板输出直接驱动,驱动电压在0-10V。文中分析其工作原理,并将其应用于相移数字散斑干涉系统中,给出实验结果。 相似文献
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基于一维空间数字相关的实时相移标定方法 总被引:7,自引:0,他引:7
摘要提出一种空间相关实时相移标定方法,用于解决存在振动和空气扰动等干扰因素情况下,相移条纹图难以准确采集和相移器的非线性对相移精度的影响问题。分析了该方法的原理和使用条件,比较了与傅里叶标定方法间的异同。实验中通过对相移器不间断驱动,使存在干扰的干涉条纹相位呈单调变化,利用两幅条纹图采集存储的时间间隔插入一维空间相关计算,实时计算出所采集条纹图与参考图之间的相关系数及其与指定的相移量余弦值之差,差值最小时得到与指定相移量最接近的相移条纹图。实验结果表明,该方法适合在稀疏等间距干涉条纹下使用,实现方法简单,运算量小,实时性强,相移器的非线性对标定结果不会产生影响,即使存在一定干扰,也能准确实时标定出相移量。 相似文献
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在波分复用光纤传像系统中,像束光纤的相关性错位误差将直接影响整个光纤传像系统的综合成像效果。本文重点分析了色散方向与光纤相关错位方向的关系对成像质量影响的规律,以及应采取的措施。 相似文献
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一种用于条带式SAR的自聚焦算法 总被引:4,自引:1,他引:3
本文将相位梯度法(Phase Gradient Algorithm,PGA)用于条带式合成孔径雷达(SAR)的自聚焦。根据条带SAR与聚束SAR回波信号差异并参考经典相位梯度法提出了一种适用于条带SAR的自聚焦算法SPGA。用这种新的条带SAR自聚焦算法聚焦所得SAR图像不会发生传统条带SAR下PGA常有的拼接问题:同时由于相位误差曲面的引入,对于任何场景SPGA均能达到良好的聚焦效果。 相似文献
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The paper presents a kind of transmission system which employs M-ary Position Phase Shift Keying (MPPSK) to send data and Phase Locked Loop(PLL)based techniques for data retrieve.With a single PLL,MPPSK demodulation is achieved,as well as carrier recovery and symbol synchronization.Firstly,MPPSK modulation method is briefly introduced.2PPSK's PSD expression is given with its optimization result.Orthogonal Phase Detector (PD) and static threshold are used for the purpose of wider phase range and simplicity in demodulation.The data rate is alterable,which is 4.65 kbps for 2PPSK and 9.3 kbps for 4PPSK in the paper.Then some indicative comparisons in Signal to Noise Ratio Symbol Error Rate (SNR-SER) are made among 2PPSK,3PPSK and 4PPSK,of which 4PPSK has proved to be optimal in ten slots each symbol conditions.And finally,it is demonstrated by system simulations that lower than 10-4 Symbol Error Rate(SER)performance can be obtained at 13 dB symbol SNR. 相似文献
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Through theoretical analysis and experiments, we discovered the quantized phase step technique existing in two cyclical movements, and the variation law of phase difference between two different frequency signals. This discovery is a major breakthrough in the traditional phase processing for researching frequency signals or cyclical movements that widely exist in nature. It has realized direct phase comparison between any signals without frequency normalization. Experimental results show that the resolution with femtosecond (fs) can be easily achieved in frequency measurement, frequency standard comparison and control on the basis of the quantized phase step characteristics. This important discovery can be widely used in navigation positioning, space technique, communication, radar, astronomy, atomic frequency standard and so on. 相似文献
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在设计运算放大器、伺服马达控制电路等带有负反馈的电路时,虽经过建模仿真,但实际电路仍然很容易产生振荡现象。该文通过分析负反馈电路设计中产生振荡现象的原因,总结出一种实用的负反馈电路稳定性评价方法——相位裕度评价法。 相似文献
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研究了高数值孔径聚焦轴对称偏振光束产生的Gouy相位在理论和应用中的重大意义。用倾斜波近似方法可以得到Gouy相位的解析表达式,但计算较繁琐不易应用。等效焦区长度和等效波长两个概念的引入使Gouy相位的计算变得非常方便,可以近似将Gouy相位看作数值孔径NA的多项式拟合函数。利用该表达式推得的焦点附近不规则的相位分布和用数值计算方法得到的结果非常相近,也验证了倾斜波近似理论的正确性。 相似文献
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Won Jay Song Song G.H. Byung Ha Ahn Minho Kang 《Antennas and Propagation, IEEE Transactions on》2003,51(6):1185-1198
We have applied the effective index method to reduce the two-dimensional (2-D) refractive index profile into the 1-D refractive index structure and modified the wave equations to obtain the paraxial wave equations. Then, transverse electric (TE) and transverse magnetic (TM) polarized fields in the curved single-mode planar waveguides are analyzed by using the scalar beam-propagation method (BPM) employing the finite-difference method with a slab structure. The bending loss in bent waveguides is analyzed for optical fields obtained from the BPM and comparisons are made between the loss for the waveguides with various radius of curvature and refractive index difference. The outward shift of the optical field, which is generated at the connection between a straight and a bent waveguide, is obtained from the results of calculation of location of the maximum optical intensity. The transition loss can be reduced by introducing an optimized inward offset at a straight-to-bend junction. The birefringence for TE and TM polarized fields in bent waveguides is calculated from the phase difference of the optical fields. The wavelength shift due to the birefringence of TE and TM polarized fields in bent waveguides is also calculated. 相似文献
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The paper presents a kind of transmission system which employs M-ary Position Phase Shift Keying (MPPSK) to send data and Phase Locked Loop (PLL) based techniques for data retrieve. With a single PLL, MPPSK demodulation is achieved, as well as carrier recovery and symbol syn-chronization. Firstly, MPPSK modulation method is briefly introduced. 2PPSK’s PSD expression is given with its optimization result. Orthogonal Phase Detector (PD) and static threshold are used for the purpose of wider phase range and simplicity in demodulation. The data rate is alterable, which is 4.65 kbps for 2PPSK and 9.3 kbps for 4PPSK in the paper. Then some indicative comparisons in Signal to Noise Ratio Symbol Error Rate (SNR-SER) are made among 2PPSK, 3PPSK and 4PPSK, of which 4PPSK has proved to be optimal in ten slots each symbol conditions. And finally, it is demonstrated by system simulations that lower than 10–4 Symbol Error Rate (SER) performance can be obtained at 13 dB symbol SNR. 相似文献