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提出并论证了混合型声光调制器衍射光的衍射级次混叠特性， 它使衍射光强中存在着驱动频率的谐波项， 此外入射光束的漂移将引起衍射光的频率漂移。分析了在外差干涉仪中应用它们对测量精度的影响， 提出了消除这些因素影响的方法： 利用双声光调制器外差干涉， 并在干涉仪的内部提取测量的参考信号。用双声光调制器的外差干涉仪可以实现纳米测量。
The diffraction order of the diffracted light of the hybrid acousto-optic modulator is presented and demonstrated. It makes the diffracted light intensity have the harmonic term of the driving frequency. In addition, the drift of the incident beam will cause the frequency shift of the diffracted light. The influence of these factors on the measurement accuracy is analyzed in the heterodyne interferometer. A method of eliminating the influence of these factors is proposed. The heterodyne interference of the two-acousto-optic modulator is used and the measured reference signal is extracted inside the interferometer. Nanometer measurements can be made using heterodyne interferometers with two-acousto-optic modulator.