Research On Wide Range And High Precision Optical Scanning Delay Line In White Light Interferometer

The distributed measurement with high resolution in white light interferometry,is a particularly important tool in the fields of precision device test and distributed sensing. As the key device of white light interferometry,the performance of the optical path scanning delay line(scan range,fluctuation of the insertion loss,etc.) is a key factor to the performance of the spatial resolution and measurement range in white light interferometry.As a integration of optical elements and machinery and electrical devices,its stability is an important part which would have great influence on the stability of the system.How to design a optical delay line with a larger scanning range,lower insertion loss and lower fluctuation of the insertion loss,and develop the corresponding debugging and stabilize method,is particularly important in application.Based on the working principles of the optical path scanning delay line, this dissertation designed a wide range optical path scanning delay line which can meet the requirements of the white light interferometry. The main contents of the dissertation are as follows.Firstly, according to the analysis of the optical elements in optical scanning delay line,we designed a matching mechanical structure.Under the overall consideration of the performance of the self-focusing lens and mirrors used in optical scanning delay line, we designed a optical mechanism to adjust and lock the location of the optial elements,and simulated its stress and strain by using Solidworks.Secondly, we developed an optical adjusting method of optical scanning delay line,and methods to improve its stability.By the use of four quadrant detector,improved the collimating precision of the self-focusing lens.In view of the 45 degree mirror pair, invented an adjusting method which can reduce the insertion loss and its volatility. The method of using multiple temperature cycle and adhesives, improved the long-term stability of optical path delay line.Thirdly,We studied how to extense the scanning range of optical delay line,and combined fixed delay fiber with continuous delay line together on the basis of the research before,and the calibration method was also studied. By the use of hardware extension, unity extension,two-way extension, fixed delay and continuous delay combine extension,differential expansion,improved the scanning range of optical delay line.On the basis of fixed delay and continuous delay combine extension, precise calibration can be made by using interferometry.Eventually, we measured the insertion loss and its volatility of the optical delay line with different scan ranges and different structures of the reflection respectively,and tested the performance of optical delay line under the working temperature and storage temperature.In addition,we tested the properties of devices in white light interferometry system with optical delay line.Above all, optical delay lines that we designed can achieve 0.3fs in resolution,contains:optical delay line with range of 200 mm, the insertion loss and volatility can achieve less than 1.5 dB and ±0.08dB; optical delay line with range of 400 mm, the insertion loss and volatility can achieve less than 1.5 dB and ±0.1 dB; optical delay line with range of 600 mm,the insertion loss and volatility can achieve less than 3 dB and ±0.15dB. In addition,the range and storage temperature of the optical delay line can achieve 800mm and -30?-60?in two-way mode, with the resolution under 0.6fs and the insertion loss under 3 dB and the volatility under ±0.15dB,which can improve the measurement range, the spatial resolution and stability of the white light interferometry system obviously.