分析了单声光移频器构成的外差式激光多普勒测振计中声光移频器驱动信号的频率稳定性和信号功率对待测振动信号的影响.为了降低声光移频器驱动信号频率漂移的影响, 提出双声光移频器构成的外差式激光多普勒测振计, 并基于直接数字频率合成技术, 以相位噪音低、初始相位可控的芯片AD9912为核心器件, 完成了声光移频器驱动信号生成及处理模块的设计.开展了双声光移频器组成的外差式激光多普勒测振计的振动测量实验,结果表明, 驱动信号生成装置可以驱动声光移频器正常工作, 且测振计的本底噪音在0~10 kHz频带范围内呈现平坦分布, 0~1 kHz频段内噪音得到明显抑制, 较单声光移频器构成的外差式激光多普勒测振计有显著改善.

The influence on the measured vibration signal caused by the frequency-stability and signal power of driver signal to acousto-optic frequency shifter (AOFS) in the high-precision heterodyne laser doppler vibrometry (HLDV) with one AOFSs was analyzed. In order to reduce the frequency drifting and the phase noise of the driver signal, the HLDV composed with two AOFSs was proposed. And based on the direct digital frequency synthesis (DDS) technology, the design of the driving signal generation unit has been completed with AD9912 which has the characteristic of adjustable initial-phase and low phase noise. The vibration-measuring experiments performed with HLDV consists of two AOFS shows that the designed generation unit is able to drive the AOFS. Meantime, compared with the HLDV with one AOFS, the noise floor from 0 to 10 kHz of the HLDV with two AOFS is flat and the noise distribution below 1 kHz has been depressed greatly.