Study On Surface Profile Measurement And Imaging Performance Test Of Wolter Type â…  Mirror

X-ray astronomy has been widely focused on in the world. Observation in solar x-ray region is functionally important for space weather forcast and exploratory research. The first domestic prototype of solar x-ray and EUV waveband imaging telescope was developed in our lab for the urgent need of imaging observation in short wavelength band of space in future. In x-ray region, the Wolter type I configuration is widely used in grazing incidence to bring x-ray into focus. The more accurate surface profile of the Wolter mirror is, the higher spatial resolution and luminous flux of imaging telescope can be obtained. This has promoted requirements for optics fabrication and metrology with very stringent tolerances on profile accuracy. Therefore, it is necessary to develop aspherical surface profile measuring device with high accuracy for Wolter mirror. My main work includes two parts: surface profile measurement and imaging test of Wolter type I mirror. The details are as follows:1. Various methods of surface profile measurement were studied. Compared with optical interference test, pencil beam scanning has more advantages and is selected to measure surface profile of Wolter mirror. As a representative instrument based on pencil beam scanning, Long Trace Profiler is analyzed in details in order to develop surface profile measuring device. 2. A prototype of surface profile measuring device, based on the principle of Long Trace Profiler, is designed and established to measure the surface profile of Wolter type I mirror. Some improvements are made to obtain higher surface profile measuring accuracy, according to the existing conditions in our lab. The properties and parameters in all parts, measuring data collection and processing algorithm are also present. The calibration experiments are done with a standard flat mirror and the results show that the prototype can achieve an accuracy of 1.7μrad RMS for slope error and 56nm PV for residual height error, which indicates that this surface profile measuring device can meet the requirement of mirror fabrication.3. Wolter type I mirror fabrication and measurement system consists of aspherical mirror fabrication instrument and surface profile measuring device of Wolter mirror. With this system surface profile of sample under fabrication can be measured on line, and real-time profile variety can be obtained. The experimental results show that sample surface profile is similar to standard profile. Maximum PV deviation is about 1.51μm from the ideal paraboloidal surface and 3.52μm from the ideal hyperboloidal surface. These data can feed back into next fabrication.4. Imaging performance test device was established to do some experiments on the sample of Wolter type I mirror. The test data are contrasted with simulation in theory, and the main causes that affect imaging performance can be analyzed. The results indicate that image degradation is caused by scattering produced from surface waviness, and the surface quality of sample mirror should be further improved.