Setting sensitivity in Talbot interferometry with modified gratings

A dual field grating has been introduced for use in Talbot interferometry. We report here results of an experimental investigation on setting sensitivity when using these gratings for testing.     

Phase-shift interferometry combined with surface plasmon resonance effect for two-dimensional bio-surface analysis

The phase-shift interferometry combined with surface plasmon resonance (SPR) effect has been studied as a novel technique used to analyze the bio-surface, which measures the spatial phase variation of SPR reflected light. The spatial sensitivity of the SPR imaging sensor is improved over the conventional SPR imaging systems based on optical intensity.     

Real time out-of-plane vibration measurement/monitoring using Talbot interferometry

In the present paper, application of Talbot interferometry for real-time vibration measurement is investigated. Experiments were conducted to measure/monitor out-of-plane motion of a vibrating loudspeaker membrane. Experimental results demonstrate that by using Talbot interferometry out-of-plane vibrations as well as phase lag between driving force and membrane oscillation can be measured.     

畴腐蚀掺镁铌酸锂可调阵列光分束器的研究

研究了不同畴腐蚀深度的掺镁铌酸锂二维六角可调阵列光分束器的分数Talbot效应.对不同Talbot分数β和不同畴腐蚀深度的阵列光分束器Talbot衍射像进行了数值模拟理论研究.模拟结果表明,Talbot分数β可以改变Talbot衍射像的周期及结构分布,而畴腐蚀深度可有效调制衍射像的光强分布.在理论研究的基础上,设计并制备了具有不同畴腐蚀深度的掺镁铌酸锂二维六角阵列光分束器,对其在不同Talbot分数β条件下的分数Talbot效应进行了通光实验研究,实现了畴腐蚀阵列光分束器对近场Talbot衍射光强分布的调制,实验结果与理论研究结果一致.     

Refractive power mapping of progressive power lenses using Talbot interferometry and digital image processing

A method of refractive power mapping of a lens is presented which is based on Talbot interferometry and utilizes a digital image processor. By adding a digital image processing system, fast measurement of a lens power distribution is feasible. A test lens is placed in front of two collinearly arranged gratings. The light passing through the test lens produces a shifted Talbot image of the first grating on the second grating and generates moiré fringes. Given the inclination angle of moiré fringes, the refractive power of the lens can be calculated. The calculation is performed using a digital image processor. This method is effective in finding the refractive power distribution of progressive power lenses.     

Temporal heterodyne shearing speckle pattern interferometry

Shearing speckle pattern interferometry is a full-field speckle interferometric technique used to determine surface displacement derivatives. In this paper, a new measurement system of real-time heterodyne shearography interferometry is presented. This system combined with heterodyne measurement, shearography interferometry and time domain signal processing technology can dynamically detect the out-of-plane displacement gradient. The principles and system arrangement are described. Using the Jones matrix, the mathematical expression of light intensity distribution passing through this system is deduced. A preliminary experiment was performed to demonstrate the performance of this new device, and simulations were conducted using the finite element method. Comparison of results shows that quantitative measurement of the displacement derivative has been achieved.     

Collimation testing using coherent gradient sensing

In the present communication, an application of coherent gradient sensing (CGS) for collimation testing of an optical beam has been proposed. In the path of the beam to be tested, a set of two identical linear Ronchi gratings is introduced. The diffracted orders from the two gratings traveling in the same direction are isolated using spatial filtering arrangement. The resulting laterally sheared wavefronts carry information regarding the defocusing errors. The grating rotation mechanism has been incorporated for collimation setting. The results of experimental investigation are presented. Improved accuracy and precision has been achieved because the requirement of maintaining the grating separation to be equal to self-imaging distance as in Talbot interferometry has been alleviated.     

Theory of the partially coherent temporal Talbot effect

The behaviour of the temporal Talbot effect under carrier partial coherence is analysed. This effect finds application as a passive method for multiplying the repetition rate of the intensity of pulse trains in first-order dispersive media. The study is based on the representation of the average intensity of partially coherent modulated light after first order dispersion as a coherence-dependent low pass filter acting on the intensity distribution obtained with a monochromatic carrier. The resulting coherence limitations are more restrictive in Talbot devices with high indices, due to the necessity of highly coherent carriers to produce a faithful reconstruction of trains by multiple pulse-to-pulse interference. Coherence limitations for architectures composed of externally modulated cw sources are analysed. Generalizations of the theory to several spectral lines, and its relation with the Collett-Wolf theorem are also reported.     

Fourier transform method for self-mixing interference signal analysis

Self-mixing interferometry (SMI) has been used to measure the distance and displacement. Although the principle of self-mixing interference is different conventional interference, we concluded that FFT analysis technique could also be used to detect the signal phase and increase the measurement precision of self-mixing interferometry.First the SMI signal is obtained by feeding the light from the target to cavity of laser diode, then it is pre-processed by an analog subtraction circuit to remove the overlapped output intensity due to the injection current modulation. Finally, SMI signal is analyzed by FFT phase detection method. Theoretical analysis and simulation calculations are presented. Experimentally, displacement of a PZT-driven target was measured with a precision of λ/50.     

任意发光类型的多色光照明下光栅塔尔博特效应的研究

利用部分相干光理论对多色光源照明下光栅的菲涅耳衍射进行了理论分析,得到了适用于任意发光类型(脉冲或连续发光)的多色光源的衍射光强的一般公式,理论结果表明菲涅耳衍射区的平均衍射光强的形式只与光源的频谱分布有关,这对借助于连续发光光源来研究脉冲光源照明下光栅的塔尔博特效应以及用来确定脉冲光源的性能参量提供了有力的参考依据。此外,详细讨论了光源的频谱分布对光栅塔尔博特效应的影响并进行了相应的数值计算。实验中通过选用不同频率的激光分别照明光栅,拍摄到对应于不同频率的衍射光强分布图像,从而间接获得多色光同时照明光栅时总的衍射光强分布。实验结果表明,理论和实验符合较好。     

Optical Texture Super-Lattices Produced by Talbot Effect at Superimposed Gratings

Fresnel diffraction on periodic gratings results in a two-dimensional periodic distribution of light intensity, also known as the Talbot effect. Here this approach is extended to the family of superimposed structures with translational symmetry, which consist of superposed spatial harmonics. The Talbot effect is demonstrated to be valid for superimposed gratings. The considered superimposed gratings provide a wide range of textures of optical super-lattices. These texture super-lattices represent a Talbot carpets with a complex motif, which can be varied by choosing structure parameters. These results provide a new functionality for structuring optical lattices and can find potential applications in a wide range of light–matter interactions.     

利用保角变换实现环形光栅的Talbot效应

Talbot效应是一种近场自成像效应,通常只有周期光栅可以产生Talbot效应,而环形光栅无法产生.本文通过引入保角变换,发现可以在环形光栅外部设计适当的折射率渐变层介质,使得其中也能够产生严格的Talbot效应,并计算了对应的自成像半径表达式.本文利用FDTD软件分别将一个环形光栅放置在真空中以及人工设计的折射率渐变层中进行了模拟,并对二者的结果进行了比较分析,发现这种折射率渐变层介质确实对点光源入射的环形光栅的自成像情况有着很好的改善.希望这一工作能够推广Talbot效应的应用范围.     

部分相干光照明下光栅的塔尔博特效应

首先利用部分相干光理论详细地分析了在部分相干光照明下光栅的菲涅耳衍射,给出了观察面上衍射光强分布的一般公式,并就光源的发光面积对光栅塔尔博特效应的影响进行了讨论,得到了光栅衍射光强的分布随着照明光源的发光尺寸的增加而逐渐变得平滑这一结论．并且,当光源发光尺寸增加到毫米量级时,光栅的塔尔博特效应将完全消失。在实验上埘不同发光尺寸的扩展作相干光源照明光栅时的菲涅耳衍射光强进行了测量,实验结果与理论分析得出的结论相符合。     

High-efficiency color separation method based on fractional Talbot effect for color liquid crystal display

Based on the fractional Talbot effect of Talbot grating, a new method with high light efficiency for color separation in color liquid crystal displays (LCDs) is proposed. The light efficiency of 85% and 89% are obtained by three- and four-step Talbot gratings, respectively, which are rather higher than that of using color filter, the traditional color separation method in color LCDs. This method has large tolerance to the position error of the color separation plane, the wavelength changes of red, green and blue colors, and the step height errors of the gratings.     

正弦相位调制双法布里—珀罗干涉术的实验研究

讨论了光纤传光、正弦相位调制的双法布里－珀罗干涉术实验结果。通过光强信号的傅里叶分析，证实基频幅值和相位均合谐振腔长度或程函变化信息，从而提出实现基频相位或幅值测量的时间间隔测量法或幅值整流基频幅值测量法。在已研制的实验装置上，测试两种方法的灵敏度阈，结果表明：作者提出的平行双通道结构和光纤传光的测试方法能补偿谐振腔温漂影响，简化信号处理过程，更适合实时测量。     

正弦相位调制双法布里－珀罗干涉术的实验研究

讨论了光纤传光、正弦相位调制的双法布里－珀罗（Ｆａｂｒｙ－Ｐｅｒｏｔ）干涉术实验结果．通过光强信号的傅里叶分析，证实基频幅值和相位均含谐振腔长度或程函变化信息，从而提出实现基频相位或幅值测量的时间间隔测量法或幅值整流基频幅值测量法．在已研制的实验装置上，测试两种方法的灵敏度阈，结果表明：作者提出的平行双通道结构和光纤传光的测试方法能补偿谐振腔温漂影响，简化信号处理过程，更适合实时测量．     

Talbot and fourier moiré deflectometry and its applications in engineering evaluation

With the aim of providing a metrical and detection method used in plate-shell mechanics and NDE, moiré interferometry (shearing interferometry) based on the Talbot effect and Fourier principle is proposed in this paper. This method does not require the use of an imaging lens, it is simple to use, and gives accurate results. The feature of this system is entirely based on the ability of an ordinary grating as the object and reference gratings, the optical differential and multiplicative element simultaneously. This will be a further step toward the realization of the aim mentioned above.     

Defect-tolerant extreme ultraviolet nanoscale printing

We present a defect-free lithography method for printing periodic features with nanoscale resolution using coherent extreme ultraviolet light. This technique is based on the self-imaging effect known as the Talbot effect, which is produced when coherent light is diffracted by a periodic mask. We present a numerical simulation and an experimental verification of the method with a compact extreme ultraviolet laser. Furthermore, we explore the extent of defect tolerance by testing masks with different defect layouts. The experimental results are in good agreement with theoretical calculations.     

High-efficiency spatial color separation method based on fractional Talbot effect

Based on fractional Talbot effect, Talbot grating is adopted to realize spatial color separation with high light efficiency. For red and green colors, a two-step Talbot grating is optimized and the light efficiency reaches over 95%. The two-step Talbot grating is fabricated and tested. Experimental results show that the Talbot grating indeed has the good ability of spatial color separation.     

Light Intensity Distribution in Laser Interference Crystallization by Using a Phase shift Grating and Talbot Effect

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