Study on Digital Readout Device of Metal Geomery Grating

摘要

According to the special characteristic of the metal grating, this paper introduces a new digital read-out device for it. Because the signal of metal grating is not as ideal as the glass's, we adapt the phase-demodulation plan in this device. This plan is not so much dependent on the quality of the waveform as the others. First, in the light of modulation theory, the displacement signal is translated into the time signal which can be measured easily; second, through A-D, a phase quantity which is proportional to the displacement quantity can be gotten; then after the process in single-chip computer, the result will be shown. In this device, using the characteristic of trigger's lock-in, we designed a high anti-disturbance phase detector. By phase follow-up and counter switching technique, the problem of missing counter's result when the direction of the moving grating is changed has been resolved.