To meet the seism detection' s require of high accuracy, high resolving power, the measurement technique of Laser Doppler and detection technique of faint signal are further researched. A differential demodulation...To meet the seism detection' s require of high accuracy, high resolving power, the measurement technique of Laser Doppler and detection technique of faint signal are further researched. A differential demodulation system of Laser Doppler is designed. Phase grating is adopt to obtain same intensity measured beams with big separative angle in the system, and by focusing the waists of two Gauss beams on the measured object with extender and collimating lens group, the smallest speckle and the superposition of plane waves are obtained. And because the big diameter lens is used to collect scattered light,the Doppler signal of high SNR is obtained. It's measured range of frequency and amplitude respectively are 0.3～1000 Hz, 1.5～5mm. And the measure accuracy of amplitude and frequency respectively are 1% and 0.4%.展开更多
文摘To meet the seism detection' s require of high accuracy, high resolving power, the measurement technique of Laser Doppler and detection technique of faint signal are further researched. A differential demodulation system of Laser Doppler is designed. Phase grating is adopt to obtain same intensity measured beams with big separative angle in the system, and by focusing the waists of two Gauss beams on the measured object with extender and collimating lens group, the smallest speckle and the superposition of plane waves are obtained. And because the big diameter lens is used to collect scattered light,the Doppler signal of high SNR is obtained. It's measured range of frequency and amplitude respectively are 0.3～1000 Hz, 1.5～5mm. And the measure accuracy of amplitude and frequency respectively are 1% and 0.4%.
