Large Aperture Plane Wave Beam Expander For Interferometer

With the rapid development of the optical field,the application of optical instruments is becoming more and more extensive,and the requirements on the surface accuracy of optical systems and corresponding optical components are also increasing.As a guarantee of processing accuracy,the detection of surface shape accuracy has become one of the focuses of research.Laser interferometry has the advantages of non-contact measurement,fast response speed,good stability,high detection accuracy,etc.It is the most commonly used detection method among several existing detection methods,but the caliber of laser interferometer is usually small and difficult to be directly applied detection of large-diameter optical components and systems.In order to solve the problem of large-aperture components and the difficulty of detecting the system,a large aperture plane wave beam expanding device for interferometer is proposed.The optical design of the device,the development of optical components and the overall assembly and adjustment were studied.The beam expansion magnification of this device is 4 times,and the outgoing beam diameter is400 mm.The following work was completed:(1)First,investigate the research status of large-diameter plane wave interferometer at home and abroad and the research status of beam expansion system.According to the design requirements,several beam expansion systems are compared and analyzed.An off-axis reflection beam expansion system is used.The initial structure of the beam-expanding system is calculated based on the two-mirror system.The structure is optimized by using ZEMAX software to obtain the design results that meet the technical requirements.(2)The calculation methods of the starting spherical surface of off-axis concave paraboloid and convex paraboloid are studied,and the processing method and the parameters of the grinding amount of each belt are given respectively.For the two mirror detection methods,the no aberration detection method is used to detect the off-axis concave parabolic mirror,and the process spherical compensation method is combined with the off-axis Hindle ball method to detect the off-axis convex paraboloid.The interferogram of each mirror surface detected by interferometer shows that the mirror surface shape RMS?? / 40(? = 0.6328?m).(3)The overall installation and adjustment of the large-aperture plane wave beamexpander for interferometers includes the assembly of mechanical parts and the installation and commissioning of primary and secondary mirrors.The research and analysis of the influence of ambient temperature on the accuracy of the device is large,and the temperature compensation structure made of Yin Steel can reduce this adverse effect.The installation and adjustment of the primary and secondary mirrors must first determine the primary optical axis,and then use the interferometer and a standard plane mirror to install and debug the primary and secondary mirrors.The measured system wave aberration meets the requirements of RMS?? / 20(? =0.6328?m).