共查询到20条相似文献,搜索用时 15 毫秒
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A microcontroller-based digital signal processing system developed for use with fiber-optic sensors for measuring pressure in internal combustion engines is described. A single distributed feedback laser source provides optical power for four interferometric sensors. The laser current is repetitively modulated so that its optical frequency is nearly a linear function of time over most of a cycle. The interferometer phase shift is proportional to the elapsed time from the initiation of a sawtooth until the sensor output signal level crosses a threshold value proportional to the laser output power. This elapsed time, assumed to vary linearly with the combustion chamber pressure, is determined by the use of a digital timer-counter. The system has been used with fiber Fabry-Perot interferometer transducers for in-cylinder pressure measurement on a four-cylinder gasoline-powered engine. 相似文献
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A phase-shift-locked interferometer has been constructed for distance measurement. A phase shift produced by sawtooth-current modulation of a laser diode is locked to a phase difference preset by polarization optics that consists of a quarter-wave plate and polarizers through an electrical feedback technique. An optical path difference can be measured from the locked sawtooth-wave current amplitude in real time. The sensitivity of the interferometer is discussed. 相似文献
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A common-path interferometer (CPI) system was developed to measure the diffusivity of transparent liquid pairs by real-time visualization of the concentration gradient profile. The CPI is an optical technique that can be used to measure changes in the gradient of the refractive index of transparent materials. The CPI is a shearing interferometer that shares the same optical path from a laser light source to the final imaging plane. Molecular diffusivity of liquids can be determined by use of physical relations between changes in the optical path length and the liquid phase properties. The data obtained by this interferometer are compared with similar results from other techniques. This demonstrates that the instrument is reliable for measurement of the diffusivity of miscible liquids and allows the system to be compact and robust. It can also be useful for studies in interface dynamics as well as other applications in a low-gravity environment. 相似文献
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A simple but reliable method, namely the working-point control by tuning the laser frequency, for the dynamic phase shift measurement in a passive homodyne interferometric fiber-optic sensor is proposed. A dc voltage calculated from the photodetector output is applied to the light source to control the interferometer at the condition of maximum sensitivity. Then the signal's phase shift can be obtained from the components of zero and fundamental frequencies. To test the method, an all polarization-maintaining Mach-Zehnder interferometer with a piezoelectric ceramic (PbZrTiO(3), or PZT) cylinder in one arm is constructed. The experimental results show that the simulation signal's phase shift generated by the PZT cylinder can be read out correctly with the method. It has the advantages of simplicities of operation, no-active element in the sensing head, and large operating bandwidth. It can be used for readout of dynamic phase shifts in various interferometric fiber-optic sensors. 相似文献
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Kim E Milner TE 《Journal of the Optical Society of America. A, Optics, image science, and vision》2006,23(6):1458-1467
We present a novel, to our knowledge, fiber-based single-channel polarization-sensitive spectral interferometry system that provides depth-resolved measurement of polarization transformations of light reflected from a sample. Algebraic expressions for the Stokes parameters at the output of the interferometer are derived for light reflected from a birefringent sample by using the cross-spectral density function. By insertion of a fiber-optic spectral polarimetry instrument into the detection path of a common-path spectral interferometer, the full set of Stokes parameters of light reflected from a sample can be obtained with a single optical frequency scan. The methodology requires neither polarization-control components nor prior knowledge of the polarization state of light incident on the sample. The fiber-based single-channel polarization-sensitive spectral interferometer and analysis are demonstrated by measurement of phase retardation and fast-axis angle of a birefringent mica plate. 相似文献
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为实现激光棒透射波前的测量,改善一般泰曼型或斐索型干涉仪测量小口径激光棒透射波前时的边缘衍射效应,研究了一种变倾角移相马赫-曾德尔干涉仪。通过调整移相反射镜的倾斜姿态,改变入射到马赫-曾德尔干涉光路的光束倾角,参考光束与测试光束的光程差随之变化,从而在相干光之间引入相移,实现了相移干涉测量。利用该干涉仪测量一根口径为Ф6 mm、长度为60 mm激光棒(Nd:YAG)的透射波前,测量结果的峰谷值(PV)为0.391λ,均方根值(RMS)为0.056λ;使用ZYGO激光干涉仪测量同一根激光棒,其透射波前的峰谷值(PV)为0.370λ,均方根值(RMS)为0.064λ。对比结果表明该干涉仪能实现光学元件透射波前的高精度检测,测试结果的一致性验证了该方案的可行性。该变倾角移相方法具有较高的移相精度和较大的移相范围,且该变倾角干涉系统中光束仅一次透过待测激光棒,可有效抑制多光束干涉现象,改善小口径激光棒的边缘衍射效应。 相似文献
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Embedded fiber-optic Fabry-Perot ultrasound sensor 总被引:2,自引:0,他引:2
Alcoz JJ Lee CE Taylor HF 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1990,37(4):302-306
A fiber-optic ultrasound sensor is presented. The sensor consists of a continuous length of single-mode optical fiber with a built-in Fabry-Perot interferometer. The acoustic pressure produces changes in the index of refraction along the interferometer cavity through the strain-optic effect, thus modulating the reflected power of the light propagating in the fiber. The dielectric internal mirrors that form the interferometer are fabricated by joining a fiber coating with a TiO(2) film at one end to an uncoated fiber by electric arc fusion splicing. Experimental results have been obtained for sensors embedded in plastic and graphite composite materials, using ultrasound waves in the range from 100 kHz to 5 MHz. Values for the optical phase shift amplitude as large as 0.5 rad were obtained at an acoustic frequency of 200 kHz for a 1.1-cm-long interferometer embedded in plastic. 相似文献
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The four path laser interferometer has been used for calibration of step gauge. Preceding studies adopting four path laser interferometer have achieved the expanded uncertainty of about 0.5 μm for 1000 mm. On the other hand, there is a concern remained that the alignment procedure seems to be tedious and the resulted uncertainty estimation becomes an empirical one. The current study aims to build an error model expressing cosine error appeared in the optical system of the four path laser interferometer. The result of model analysis points out that conventional error estimation may cause non-negligible under estimation on cosine error. The model analysis performed to clarify error propagation of angular deflection of plane mirrors of the four path laser interferometer requires thorough consideration for estimating its contribution to the uncertainty. 相似文献
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In an absolute gravity meter, a laser interferometer measures the position of a test mass that is falling ina vacuum. The calculated value of gravity is the average acceleration of the mass during a set ofdrops. Since systematic accelerations of the optical system will bias the measured value of gravity,various interferometer geometries have been implemented in the past to isolate the optical system fromground motion. We have developed and tested a low-finesse fiber-optic extrinsic Fabry-Perotinterferometer that is fixed to the mass of a critically damped seismometer in which the effects ofsystematic ground motion and acoustic vibrations are reduced. 相似文献
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Jacquin O Lacot E Glastre W Hugon O Guillet de Chatellus H 《Journal of the Optical Society of America. A, Optics, image science, and vision》2011,28(8):1741-1746
Using an Nd:YVO? microchip laser with a relaxation frequency in the megahertz range, we have experimentally compared a heterodyne interferometer based on a Michelson configuration with an autodyne interferometer based on the laser optical feedback imaging (LOFI) method regarding their signal-to-noise ratios. In the heterodyne configuration, the beating between the reference beam and the signal beam is realized outside the laser cavity, while in the autodyne configuration, the wave beating takes place inside the laser cavity, and the relaxation oscillations of the laser intensity then play an important part. For a given laser output power, object under investigation, and detection noise level, we have determined the amplification gain of the LOFI interferometer compared to the heterodyne interferometer. LOFI interferometry is demonstrated to show higher performance than heterodyne interferometry for a wide range of laser powers and detection levels of noise. The experimental results are in good agreement with the theoretical predictions. 相似文献
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A great amount of phase fluctuation was observed in the dual-wavelength heterodyne interferometer that we have developed. Through analyses and experiments, we found that this fluctuation was caused by polarization mixing in the interferometer. The errors originating from the polarization mixing were also found to be the first or second harmonic versus the phase change of one mode of the laser in the optical path difference and might become substantial in value. Measures that reduce the polarization mixing and improve the precision of the interferometer are given. 相似文献
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Frequency changes induced by bias or temperature modulation of injection diode lasers can provide an economical and effective method of applying phase-stepping interferometry to optical metrology. However, the intrinsic frequency instability of these devices limits their use in gauge block interferometry where precise and repeatable phase steps must be maintained simultaneously on two discontinuous surfaces and over relatively long path lengths. We demonstrate a method using a visible injection diode laser, the frequency of which is locked by using a Fabry-Perot interferometer. Small changes to the length of the Fabry-Perot interferometer shift the frequency of the laser producing proportional and repeatable phase steps to the gauge block interferogram. This method has been successfully implemented with a Fizeau-type gauge block interferometer with a phase measurement resolution of 0.005 lambda. The phase data are then processed to map the surface form of gauge blocks up to 100 mm in length and to objectively assess surface shape parameters. 相似文献
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The path imbalance (PI) of the two-arm fiber-optic interferometric sensor is a substantial parameter; a precise value of millimeters is required. Currently the precision reflectometry and the millimeter optical time-domain reflectometry are used to measure the tiny optical path difference, but the performances of these measurements are limited from the length and the resolution of the PI. We propose a new method accomplished by interferometer to accurately measure millimeters to within a few decimeters of the PI. 相似文献
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Chou C Teng HK Tsai CC Wu JS 《Journal of the Optical Society of America. A, Optics, image science, and vision》2008,25(11):2630-2635
A differential-phase decoder (DPD) together with a polarization common-path optical heterodyne interferometer is set up. Based on this interferometric configuration and a novel balanced-detector scheme, the performance of the quantum-noise-limited differential-phase decoder is demonstrated and analyzed. The minimum-detectable differential phase is on the order of 10(-7) rad/sqrt Hz when a 2.5 mW He-Ne laser is used. Verified experimentally, the DPD is immune to the common-phase noise induced by an electro-optic phase modulator or by thermal disturbance within the interferometer. This signifies that the minimum-detectable differential phase can become 10(-8) rad/sqrt Hz if a 300 mW continuous wave laser is employed instead. 相似文献
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Camp JB Yamamoto H Whitcomb SE McClelland DE 《Journal of the Optical Society of America. A, Optics, image science, and vision》2000,17(1):120-128
We present a method by which the effect of laser field variations on the signal output of an interferometric gravitational wave detector is rigorously determined. Using the Laser Interferometer Gravitational Wave Observatory (LIGO) optical configuration of a power recycled Michelson interferometer with Fabry-Perot arm cavities as an example, we calculate the excess noise after the input filter cavity (mode cleaner) and the dependence of the detector strain sensitivity on laser frequency and amplitude noise, radio frequency oscillator noise, and scattered-light phase noise. We find that noise on the radio frequency sidebands generally limits the detector's sensitivity. 相似文献
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É. I. Alekseev E. N. Bazarov Yu. A. Barannikov V. P. Gapontsev V. P. Gubin I. É. Samartsev N. I. Starostin 《Technical Physics Letters》1998,24(9):719-721
A new optical system is proposed and investigated experimentally for a Sagnac fiber interferometer in which the excess noise
of the wide-band radiation source is suppressed. A tenfold improvement in the sensitivity of a fiber-optic gyroscope with
an erbium/ytterbium fiber superfluorescent light source was achieved experimentally. It is shown that the identity of the
polarization characteristics of the interferometer channels plays an important role.
Pis’ma Zh. Tekh. Fiz. 24, 30–35 (September 26, 1998) 相似文献
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激光偏振干涉光路的非线性分析计算 总被引:6,自引:0,他引:6
偏振干涉光路两臂光程差的变化和合成干涉信号的相位变化,理论上具有线性关系,可以对引起光程差的任何微小量进行测量。实际上光路光学元件性能及调整并不理想,形成了二者的非线性关系。本文分析计算了各光学元件形成的非线性及这些元件综合形成的非线性,给出了适用于各种情况下的计算公式,并提出了光路的调整方法。 相似文献