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Reconstruction and prediction of multi-source acoustic field with the distributed source boundary point method based nearfield acoustic holography

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Science China(Technological Sciences) 2004年第2期47卷 216-228页

作者： BI Chuanxing CHEN Jian CHEN Xinzhao Dynamic Measuring Center Hefei University of Technology Hefei 230009 China Dynamic Measuring Center Hefei University of Technology Hefei 230009 China Dynamic Measuring Center Hefei University of Technology Hefei 230009 China

In a multi-source acoustic field, the actual measured pressure is a scalar sum of pressures from all the sources. The pressure belonging to every source cannot be separated out with the existing techniques. Consequently, routine formulas cannot be used to reconstruct the acoustic source and predict the acoustic field directly. In this paper, a novel theoretical model of reconstruction and prediction of multi-source acoustic field in the distributed source boundary point method (DSBPM) based nearfield acoustic holography (NAH) is established. Three different methods, namely combination method with single surface measurement, combination method with multi-surface measurement and elimination method with multi-surface measurement, are proposed to realize the holographic reconstruction of sources. With these methods, the problem of reconstruction and prediction of acoustic field existing multiple coherent sources synchronously is solved effectively. Using the particular solutions constructed by the DSBPM to establish the vibro-acoustic transfer matrix, the calculation time, calculation precision and calculation stability are improved. These methods are valuable in localizing acoustic source and predicting acoustic field in engineering field.

关键词： acoustic holography, boundary point, distributed source, acoustic radiation.

Theoretical and experimental investigation of holographic reconstruction and prediction of multi-source hybrid acoustic field

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Science China(Physics,Mechanics & Astronomy) 2005年第3期48卷 282-299页

作者： BI Chuanxing CHEN Jian CHEN Xinzhao YU Fei LI Weibing Dynamic Measuring Center Hefei University of Technology Hefei 230009 China Dynamic Measuring Center Hefei University of Technology Hefei 230009 China Dynamic Measuring Center Hefei University of Technology Hefei 230009 China Dynamic Measuring Center Hefei University of Technology Hefei 230009 China Dynamic Measuring Center Hefei University of Technology Hefei 230009 China

Study on a multi-source hybrid acoustic field is very important for nearfield acoustic holography (NAH) to be applied in the practical engineering field. In this paper, two methods based on the distributed source boundary point method (DSBPM) for holographic reconstruction and prediction of multi-source hybrid acoustic field, namely combination method with single surface measurement and combination method with multi-surface measurement, are proposed. Then, an experiment on two coherent speakers is carried out. By comparison of the reconstructed and predicted results and the actual measured results, the validity of the two methods and the superiority of the combination method with multi-surface measurement are proved. Considering the high sensitivity of the reconstructed results to measurement errors, the Tikhonov regularization method is proposed to stabilize the reconstruction procedure and restrict the influence of errors. And then, the optimal reconstructed results can be obtained and the reliability of holographic reconstruction and prediction is assured.

关键词： acoustic holography, boundary point, distributed source, acoustic radiation, regularization.

Experimental study on polarization holographic storage in genetic mutant BR-D96N film

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Science China(Physics,Mechanics & Astronomy) 2004年第3期47卷 284-292页

作者： MENKE Neimule Norbert HAMPP State Key Laboratory of Transient Optics Technology Xi'n Institute of Optics and Precision Mechanics Chinese Academy of Sciences Xi'n 710068 ChinaInstitute of Physical Chemistry University of Marburg D-35032 Marburg Germany

Recording with both parallel and orthogonal linearly polarized lights, polarization holographic storage in genetic mutant BR-D96N film is reported with both transmission type geometry and reflection type geometry. Polarization properties of diffraction light and scattering light are discussed for two different cases, parallel polarization recording and orthogonal polarization recording. It shows that, compared with recording with parallel polarization lights, orthogonal polarization holography can separate the diffraction light from the scattering noise, therefore improving the signal-to-noise ratio. It also shows that, compared with reconstruction with reference light, reconstruction with phase conjugated wave of the reference light can improve the signal-to-noise ratio of the reconstructed diffraction image, and also the wave-front aberration of the object light introduced by irregular phase object in the optical pass-way can also be corrected effectively, which ensures that the reconstructed diffraction image has a better fidelity. The preliminary angle-multiplexed volume holographic storage multiplexed by transmission type geometry and reflection type geometry is demonstrated in the BR-D96N film. Experiment shows that there is no cross-talk between the two pages of images except for some scattering noises.

关键词： polarization holography, BR-D96N, photochromism, phase conjugation, photo-induced anisot-ropy.