A fast and ultra-precision laser heterodyne interferometry signal processing method based on digital delay line loop

To achieve higher dynamic resolution of laser heterodyne interferometry, a new signal processing method based on digital delay line technology is proposed. To implement ultra-multiple electronic subdivision, the multiple frequency of the reference signal which is generated from an analog phase-lock loop is passed through a multi-tap digital delay line. On every positive edge of the measurement signal, each tap of the delay line is captured and decoded to obtain the exact occurrence time. And according to the reference period, the system can also provide a real time output of the displacement results. Simulations and experiments show that using a laser heterodyne interferometry with its beat frequency of 1MHz, the system can provide a dynamic position resolution of 0.83nm at velocities up to 260mm/s by using a 64 multiple analog phase-lock loop and a 6-tap digital delay line, the update rate of the displacement positions is up to 100KHz.