Research On Fiber Interference For Large Range Absolute Distance Equipment

The technology of non-contact, large-range and high-accuracy absolute distance measurement plays an important role in nowaday measument technology with a bright future in application. Although the absolute distance measurement technology based on the principle of optical fiber quasi-white light interferometry develops very raplidly, the technology concering large-range distance measument has not been reported. The subject, "large-range optical fiber quasi-white light absolute interferometry distance measurement technology", is financed by National Natural Science Fund (Project No.50005014), which develops a high-accuracy, portable, absolute distance measurement technology based on the optical fiber quasi-white light interferometry. The large-range distance measurement above 10 meters can be realized by use of the short-scanning guide.The thesis mainly discusses about contents described as follows:The triple measuring range multiplication system is designed and the optical switch device is introduced to the optical fiber interferometer field for the first time. Because of triple range multiplication optimal design, the measuring range of optical fiber absolute distance measurement instrument is enhanced above 10 meters, which meets the demand of the short scanning guide and large-range measurement in deed.The fiber self-calibration technology in the triple measuring range multiplication system is developed, which finishes the self-calibration of the original optical difference of the optical fiber groups by using the system scanning interferometer. The system uses the self scanning interferometer optical wavelength to fulfill the transmission of the length reference, and the anti-interference capability of system is enhanced greatly.The optical fiber quasi-white light interference signal model under the afflux of semiconductor laser current is established, and the influence on coherent length and optical fiber interferometry locating precision, which are caused by different modulating methods and depths of the semiconductor laser, is researched in detail.The digital processing technology to obtain the high precision locating signal is researched. The characteristics of the orientation signal is analyzed, the magnifying circuit for the weak interferer signal and the processing circuit of the optical fiber quasi-white light interferometer signal are made.The structure optimization and miniaturization scheme for the measurement system are deeply researched, the prototype of optical fiber quasi-white interferometer is developed. Through miniaturization design of optical system and scanning system, the fiber absolute distance measurement interferometer is reduce to volume of 600mm×250mm×250mm. FPGA technology is exploited to optimize circuit, which not only increases reliability, but also improves precision. Furthermore, the speed of data processing is increased, and available for subsequent processing and handling on account of the optimizing design of computer interface software module.