Research On Long-range Grating Displacement Measurement System With Nanometer Resolution

With the development of the science and technology, nano-measurement technology has boomed in most areas. Displacement is one of the most basic physical quantities, and the two main means of modern precision displacement measurement technology are laser interferometry and grating measurement. Compared with the laser interferometer, the grating measurement is less susceptible to the environmental interference, easier to be miniaturized and much cheaper, so it has been widely studied and applied. Although the research and application on grating measurement have already been quite mature and the gratings have been massively produced both at home and abroad, the resolution is lower than the laser interferometry. So the research on the grating displacement measurement system with nanometer resolution is of great significance.The grating displacement sensor is used as core element, and a long-range grating displacement measurement system with sub-nanometer resolution and nanometer stability is set up with digital filter. The main work is as follows:1) According to the target, the bearing mechanical structures of grating ruler, motor and guide rail have been designed.2) The signal processing circuit with higher signal noise ratio (SNR) was designed, which is composed of differential amplification, DC elimination module, normalization processing, filter and so on.3) Based on the subdivision method of integrated hardware and software, the corresponding pulse counting circuit has been designed. The displacement measurement procedure has been programmed successfully combined with the data acquisition card. The noise of the output signal was greatly reduced by the digital fiter. The resolution of the system has been improved.4) The experimental system has been set up to test the system performances. The measurement error in full range has been compensated.Experimental results show that:the resolution of grating displacement measurement system can achieve sub-nanometer level within 220mm, and its stability is in nanoscale within 60 min. Its measurement error in full range can be kept within ±0.5μm after compensation.