Fringe Locking in a Laser Diode Interferometer by Optical Feedback During Modulation of Injection Current

A fringe locking phenomenon in a two beam interferometer using a semiconductor laser subject to optical feedback was, whose injection current is modulated. When a path difference of the interferometer is sufficient, fringes taken by a charge coupled device camera are seen to be stationary and the rms fluctuations of fringe phase is reduced to as low as 0.2ϖ radians from more than 8ϖ radians without the optical feedback. The rms phase fluctuation is independent of frequency and amplitude of the current modulation. The fringe locking has also been observed in the presence of both injection current modulation and piezoelectric transducer mirror vibration.     

An automatic processing technique for accurate surface form measurement

A single shot algorithm using a Fizeau interferometer was used to measure the form profile of a spherical smooth surface by means of fringe thinning process, which plays an important role in fringe patterns analysis. In this paper, an automatic processing technique based on the fringe thinning process is presented. The circular interference fringe pattern of the spherical smooth surface captured by the Fizeau interferometer was corrected by using the flat fielding method and then processed. Based on the fringe thinning and the assignment of the fringe orders, the information on the fringe feature was recovered automatically and the interference wavefront was reconstructed by the Zernike polynomial fitting method. The results were compared with the results measured by Bünnagel method, and the results were in good agreement. This means that the single shot algorithm is reliable, fast, and less sensitive to vibration and turbulence in surface form measurements. Simulation fringes with the ray tracing technique were obtained to match the practical fringes.     

使用相位共轭光精密测量粗糙面物体的振动振幅

提出了一个用于测量粗糙面物体振动振幅的自抽过相位共轭干涉仪,粗糙面反射光的波前失真由相位共轭修复,用这个干涉仪屯一个有粗糙表面的不锈钢片的振动幅分布。     

Holographic interferometry using a reference wave with a sinusoidally modulated amplitude

A method of holographic interferometry which uses an amplitude-modulated reference wave is proposed for investigating vibration phases. Sinusoidal amplitude modulation of a reference wave yields hologram fringes which are characterized by a function J²₁(α)cos²Δ, where α and Δ are related to vibration amplitudes and phases on object points, respectively. The resultant fringes indicate that vibration amplitude information and phase information are stored separately. The phase information of the vibration is easily obtained as brightness variations of the fringes, independently of the amplitude information.     

Fringe Locking in a Laser Diode Interferometer under Both Mirror Vibration and Injection Current Modulation

We have found that the fringes in a laser diode interferometer can be locked even in the presence of mirror vibration and injection current modulation. A theoretical analysis explains the fringe locking phenomenon. The dependence of wavelength change on both PZT (piezoelectric transducer) mirror vibration and the injection current variation are calculated using a model of coupled resonators consisting of the laser cavity and the interferometer. The fringe phase change caused by the vibration and modulation of the current is derived from this model, and was proven to be suppressed within much less than 2ϖ in excess of an integer multiple of 2ϖ.     

球面的快速测量与非球面的快速拼接

利用立式车间用球面干涉仪实现比较法球面面形测量，一次调整好以后可以达到多片快速测量，避免复杂的调整，通过监示器看到光圈；并可以通过条纹扫描技术实现光圈数Ｎ及局部光圈数ΔＮ的自动客观判读；对于低陡度非球面的多块拼接，可以籍助“非球面特征干涉图”实现快速初步拼接，然后再用每个子孔径的相位探测实现整个孔径的拼接，并可以通过数字的测量与波面相减自动获得非球面的面形误差。     

Real-time surface shape measurement by an active interferometer

We have succeeded in video rate analysis of fringes stabilized by an active interferometer placed outside optical benches. The interferometer uses the closed loop control of injection current of a laser diode to compensate for fringe movement that is detected by a spatial filtering detector. A video image of the locked fringes with tilt is supplied to the real-time fringe analyzer that delivers unwrapped phase distribution from the three phase shifted fringes generated by the electronic moiré method. For a concave mirror of 130 mm diameter placed on a wooden desk we observed the repeatability of λ/60 for P-V surface error of λ/5.     

X-ray interferometric Fourier holography

An X-ray interferometric Fourier holography was proposed and theoretically investigated. X-ray Interferometric Young fringes and the reconstruction of an object image were investigated by the Fourier transform method. It was shown that on the output surface of the analyzer crystal (the third plate of the interferometer) the interference pattern of two slits gives X-ray interferometric Young fringes. An expression for the period of X-ray interferometric Young fringes was obtained. The subsequent reconstruction of the slit image as an object is conducted by means of the Fourier transform method of intensity distribution on the hologram. Three methods for reconstruction of the function of complex transmission of the object are presented: an analytical one–the approximate method, the iteration method and the step-by-step approach. As examples a recording of X-ray interferometric Fourier hologram and the reconstruction of the function of complex amplitude transmission of a beryllium circular cylinder are given.     

远距离环状干涉条纹形成的初步实验

 针对远距离激光干涉成像中条纹的形成进行了研究。分析了成像所需条纹的特点，表明干涉条纹成像系统的带宽决定于条纹的空间带宽。讨论了传统的迈克尔逊干涉仪结构在激光干涉成像中应用的不足之处，并在迈克尔逊干涉仪的基础上，提出一种变形的光路结构，用于在远距离上形成圆对称环状干涉条纹，同时报道了利用该变形结构在约50m的距离上观察到的条纹，表明了该光路结构的可行性。     

Vibration Analysis by Phase Shifting Digital Holography

Phase-shifting digital holography has been used for the study of vibrating objects. The time-averaged complex amplitude of Fresnel diffracted field due to a vibrating object was obtained by using a three-step phase-shifting algorithm. Taking the inverse Fresnel transform of the complex amplitude resulted in an image of the object superimposed with Bessel fringes. The Bessel fringes are contour map of the vibration amplitude. By sinusoidally modulating the phase of the reference beam at the vibration frequency, the brightest fringe could be shifted to points of interest, thus extending the measurable range of vibration amplitude.     

光源相干长度对光纤Fabry—Perot干涉的影响

从数值上分析了光源相干长度对光纤Fabry-Perot干涉的影响。推导了光源在理想情况和非理想情况下的光纤Fabry—Perot干涉模型,通过计算机模拟了干涉信号,指出在非单色光源下,干涉条纹失去周期性,随着腔长相干长度比增加干涉条纹的变化幅度减小,最后演化成一条直线,条纹的可见度也慢慢趋近于零。综合考虑了光纤的耦合效率和光源的非单色性对干涉信号的影响,随着腔长的增加,干涉信号的幅值和变化幅度都在减小,信噪比变差。要得到好的干涉信号,腔长不宜选择过大,必须使光源的腔长相干长度比值低于0．1。     

The investigation of high frequency vibration modes of PZT-4 transducers using ESPI techniques with reference beam modulation

In this paper the experimental vibration amplitudes together with the vibration modes of the PZT-4 transducer radiating front face are presented for generation in various media. The studies were carried out using an electronic speckle pattern interferometer (ESPI) with reference beam modulation to give resolution down to 20 Å of surface amplitude. Analogies are drawn between these transducers and the resonant vibration modes of thin plates. The relationship between the surface vibration amplitudes and the radiation beam pattern of the transducers is also presented.     

光纤Fizeau干涉仪的声发射检测研究

验证了一种基于光纤Fizeau干涉仪的声发射传感器,可用于固体表面传播的超声波的检测.这种传感器的特点是能够精确地检测由固体表面传播的超声波产生的微弱振动.当超声波信号通过光纤传感器到达探测器时,干涉仪的输出光强度受到了超声信号的调制.通过检测干涉仪的输出光强度并利用Fourier变换,测得了超声信号的振幅和频率.对传感系统的相位调制特性进行了仿真,并对实验结果进行了分析.     

光学平移装置行进横向漂移的干涉法测量

应用泰曼-格林干涉仪测量步进电机控制下光学平移装置行进时的横向漂移,鉴于步进装置行进时的震动和它引起的探头抖动干扰,提出一种基于小波变换滤波的条纹细分技术,以利于信号识别和精确测量．     

Light-pulse atom interferometry in microgravity

We describe the operation of a light pulse interferometer using cold ⁸⁷Rb atoms in reduced gravity. Using a series of two Raman transitions induced by light pulses, we have obtained Ramsey fringes in the low gravity environment achieved during parabolic flights. With our compact apparatus, we have operated in a regime which is not accessible on ground. In the much lower gravity environment and lower vibration level of a satellite, our cold atom interferometer could measure accelerations with a sensitivity orders of magnitude better than the best ground based accelerometers and close to proven spaced-based ones.     

THz干涉测量用于障碍物后振动传感的研究

为探索THz干涉技术用于障碍物后振动传感的可行性,采用工作波长214.58 μm （对应频率约1.4 THz）的CO2激光器泵浦气体太赫兹源搭建了一套基于迈克尔逊干涉仪结构的THz干涉测量装置,实验研究了薄纸板遮挡后敲击目标镜产生的微小振动,利用相位分析法和频谱分析法对振动干涉信号进行处理,得到了振动位移随时间的变化以及不同时段振动频率的分布情况,测得的峰峰值振幅最小为7.98 μm,最大为17.54 μm,振动峰值速度为2.7 mm/s,振动频率最小21 Hz,最大58 Hz.研究结果表明THz干涉测量技术能有效克服传统振动传感技术无法穿透障碍物的缺点,是一种简便有效的障碍物后振动传感的新型手段,预示了THz技术在振动检测相关领域的广阔应用前景.     

基于多级组合棱镜提高激光中心波长检测精度的研究

为了在保证抗干扰能力不下降的条件下提高对激光中心波长的检测精度,设计了多级组合棱镜系统,并提出了多级组合棱镜的干涉条纹拼接处理方法及相位耦合的计算公式.通过计算多级组合棱镜的干涉图强度、光程差函数及光谱分辨率,分析了采用三块子棱镜的组合结构的光谱获取,给出了用于分段干涉条纹拼接的处理方法及步骤,最终光谱分辨率可达2.8...     

Interferometry based on Lau effect with a grating registered in a photorefractive crystal

The use of a grating in the form of modulation of birefringence in a BSO crystal in a novel Lau interferometer set-up is proposed. The system behaves as a conventional Lau interferometer implemented by using two amplitude gratings. Moreover, it permits control of the visibility and provides a contrast inversion of the interferometric fringes by rotating a polarizer. Two alternative experimental arrangements with similar performance are presented. A theoretical approach is outlined and the predicted behavior is confirmed by results obtained under different experimental conditions.     

Stroboscopic holographic interferometry of vibration with space-variant phase

A method employing pulsed illumination for the holographic analysis of vibration with space-variant phase is described. Superimposition of two stroboscopically recorded interference patterns to get the amplitude and the phase of vibration at the intersections of fringes is suggested. Contour maps of these two quantities over the entire object surface can then be prepared by interpolation. Detailed solutions are presented for single and double frequency vibrations.     

基于适度光反馈自混合干涉技术的振动测量

光反馈自混合干涉技术是一种新浮现的有别于传统双光束干涉的一类新的测试技术。为了在适度光反馈下进行振动的精密测量,提出了一种基于适度光反馈自混合干涉技术的振动测量方法。经对光反馈自混合干涉信号条纹分析,发现通过选定合适的光反馈水平及激光器线宽展宽因数,可以得到锯齿干涉条纹。这种干涉信号不仅包含振动幅度信息也包含振动方向信息。该振动测量方法利用锯齿干涉条纹的特点,首先通过条纹记数实现大范围振幅粗测,具有半波长位移分辨力;然后基于适度光反馈下小数条纹的特点,给出了小于半波长位移测量的线性表达式,从而实现位移的精测。仿真计算表明,该方法可以实现大量程高分辨力振动位移测量,在叠加20 dB的噪声下,振幅测量相对误差平均为0.5%。