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1.
The non-linearities in a heterodyne laser interferometer system occurring from the phase measurement system of the interferometer and from non-ideal polarization effects of the optics are modeled into one analytical expression which includes the initial polarization state of the laser source, the rotational alignment of the beam splitter along with different transmission coefficients for polarization states and the rotational misalignment of the receiving polarizer. The model is verified using a Babinet Soleil Compensator allowing a common path for both polarization states and thereby reducing the influence of the refractive index of air. The verification shows an agreement of the model with measurements with a standard deviation of 0.2 nm. With the use of the model it is confirmed that the mean of two polarizer receivers can reduce the effect of non-linearity. However, depending on the accuracy of the polarizer angles, a second-order non-linearity remains. Also the effect of rotational misalignment of the beam splitter can not be reduced in this way.  相似文献   

2.
W. Hou  R. Thalmann   《Measurement》1994,13(4):307-314
An interference refractometer for absolute measurement of the refractive index of air has been developed. It is essentially based on components of a commercial Zeeman type laser interferometer system and uses a differential interferometer and a vacuum chamber with four measurement cells. The resolution and accuracy of interference phase interpolation is improved by an electronic phase meter and a detection technique which compensates for interferometer non-linearity. The system has been designed for an accuracy of a few parts in 108. Experimental investigations of individual components and comparison measurements with pure gases, with Edlén's formula and with the BCR interference refractometer confirm this goal.  相似文献   

3.
光学外差干涉法检测微弱超声振动的研究   总被引:1,自引:1,他引:0  
设计一个具有较高检测灵敏度的光学外差干涉系统,用于检测微弱超声振动信号。采用相干性高的线偏振光作为光源,提高有效干涉强度;利用光阑消除光学噪声,有效控制回授光对光路的影响;以1级光作为参照,使光路调节简单易行。用主频为62.42KHz、幅值为74V的方波信号激励超声探头作为振动信号源,测得振动信号频率和幅值分别为62.38KHz和76.4mV。结果表明该系统能满足微弱超声振动检测要求。  相似文献   

4.
The improvement and validity of shock measurements using only the laser head (heterodyne laser interferometer) of a commercial laser Doppler vibrometer was investigated by comparing acceleration waveforms measured by a homodyne laser interferometer with those measured by a heterodyne laser interferometer. The acceleration waveforms were generated from the displacement waveforms obtained with a reference quadrature homodyne laser interferometer by applying a numeric differentiation process twice. The differences between the two acceleration waveforms were found to be small with the measurement uncertainty in case of high acceleration level. In a further investigation, the accuracy of the shock measurements taken by the homodyne and heterodyne laser interferometers were compared in computational simulation. The results indicated that the accuracy of the heterodyne laser interferometer was superior to that of the homodyne laser interferometer.  相似文献   

5.
A bi-directional fringe counting interference refractometer has been developed primarily to measure the refractive index of air so that the accuracy of laser length measuring interferometer systems used in the free atmosphere can be maintained. Two signals suitable for electronic counting in phase-quadrature and sinusoidally related to path difference are produced by a technique that does not require any form of modulation and yet has the advantages of a modulated system. This refractometer is cheap to produce and easy to set up and align. Measurement sensitivity of 2.5 parts in 107 for the refractive index of air can be obtained directly from the counting signals and this has been further improved by fringe sub-division. Comparisons with calculated values indicate that the refractometer can measure ambient refractive index in a laboratory without temperature control with an uncertainty approaching 1 part in 107  相似文献   

6.
We describe the combined methods of displacement heterodyne laser interferometry with wavelength tracking based on a Fabry-Perot cavity to correct the instantaneous wavelength in air. The optical frequency of the interferometry source was locked to the resonance peak of an open cavity, directly linking the refractive index changes to frequency changes. Using this method, refractive index changes are compensated by an appropriate change in the laser frequency in real time, eliminating the limitations with environmental parameter measurement bandwidth uncertainties associated with equation-based corrections. In this paper, the principles of the system are explained and experimental results showed a difference of 2 nm compared with traditional equation-based techniques. The measurement uncertainty and practical considerations for implementation are also discussed.  相似文献   

7.
为准确测量声场分布,研究了基于激光测振仪的声场直接测量技术。基于声音在空气中传播时会引起空气折射率周期性变化的原理,利用激光测振仪测量了激光通过声场时激光光程受空气折射率的调制发生周期性变化产生的振动速度。由于声场在激光方向上的投影即为激光测振仪测得的振动速度,测量了声场在不同投影方向上的振动速度,再由Radon逆变换重构声场复振幅分布,从而实现了对声场的直接测量。文中实验测量了2kHz声场引起的振动速度振幅分布和相位分布,进而重构得到声压振幅分布和瞬时声压分布。测量得到空间分辨率为2cm,声压振幅最大为0.026Pa,对应的声压级为62.3dB。实验结果表明,基于激光测振仪的声场分布直接测量方法是可行的,该方法解决了现有麦克风阵列接触式测量声场存在的问题。  相似文献   

8.
9.
The low vibration of air spindle is a very important thing to achieve nanometer accuracies in the products of machined parts in nano-machining. Compared to the common air pockets with constant depth used in air cells of ultra-precision machines, this paper studied some special air pockets including five variable depth modes: flat, conical, pyramidical, spherical with two sphere radii. Considering rotational speed as well as these parameters, 18 experiments have been committed using a lathe machine. From experiment results, the air spindle with air pockets of pyramidical depth at a low rotational speed has minimum vibrations.  相似文献   

10.
Measurement of vibration is a vital factor that limits the precision and accuracy of machining of micro and macro components. In this paper, a novel technique for measurement of vibration is proposed using an acousto-optic modulator, which highlights an improved approach in measuring vibration in the subnanometre range. An experimental comparison was made with a laser Doppler vibrometer. This novel concept is proposed for application to a precision machine tool to measure the vibration on the machine bed induced during the machining process and by the external environment, which can be compensated for by in-process techniques. This novel measurement technique can also be applied for the precision measurement of the stage movement in ultra-precision machines to a subnanometre resolution.  相似文献   

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