Experimental Study On The Laser Interference Detecting Device

With the development of modern industry, the detection system is required high resolution, large range, high detection efficiency, etc., but at this stage, most of the measuring instruments can't still meet the requirements of both high accuracy and large measurement range. The detecting equipments using the principle of laser interference, can not only achieve high accuracy and large measurement range, but also trace measurements to the laser wavelength, which brings convenience in unifying the traceability of a variety of nano-scale measurements and has great significance.The issue replaced light source of Ukraine interferometer with laser, then designed and built a laser interference detection device. Finally, calibrated the resolution and range of the device through calibration experiments, and verified the reliability of measurement results through roundness error measurement experiments.Firstly, based on studying precision measurement technology and several typical interferometers, Ukraine interferometer was transformed, light source replaced with He-Ne laser to transplant advantages of laser interferometer. The photoelectric conversion method was used in interpretation of interference fringes, two orthogonal interference signals were extracted by using photodiode to detect light intensity changes in fringes, finally, the information of fringe movement were known by processing signal, and achieved the aim of detecting displacement.Secondly,selected optoelectronic devices, designed mechanical structure of optical interference and signal processing circuit. The amplification and filter circuit was designed to extract the interference signal; The error processing problem produced when signal jitter near the set comparison value, therefore, a dual-threshold shaping circuits was designed to solve it; Studied the methods for discerning direction and subdividing interference fringes, and designed a basis discerning circuit and 4-subdivision discerning circuit. A direction discerning counter was designed by using MCU, and count value was displayed on computer by using the serial interface.Finally, completed experiment after built up and debugged the detecting device. Through the interferometer calibration experiment, the measurement range of the detecting device was figured out 1.097mm, and the resolution of basic discerning and 4-subdivision discerning circuit were respectively 146nm and 74nm. Then completed shaft roundness error measurement experiment, the results corresponded with the actual situation, which verified its reliability.