| Space extreme ultraviolet telescope(EUT) will consist of four single-channel telescopes, which will be bound together and observe the same part of the solar at the same time in 13.0nm 17.1nm, 30.4nm and 19.5nm respectively. Because of the influence of alignment error on ground and launch vibration, it is impossible for EUT to keep four channels parallel perfectly. And this will bring error of observation. The error has an effect on image registration and synthesizing .For synthesizing high resolution image, the angles between channels need be measured, then calibration of EUT in orbit will be carried out. By this, the error of observation will be reduced. The precision requirement of angles measurement is 0.1 arc second. Angles measurement can be substituted by translation measurement between images in detectors.In this paper, two algorithms-part edge detecting and phase correlation-are proposed to measure translation between images in detector. Translation between images can be decided by position variety of characteristic point in images. Because of influence of resolution for CCD, measuring accuracy of translation is pixel level, which can not satisfy measuring accuracy demand. In order to solve the problem, CCD is subdivided with paraboloid surface fit and Newton interpolation. Thus measuring accuracy of translation can attain sub-pixel level. Experiments of translation- measurement were made and image process software is programmed. The results show that translation measuring accuracy of part edge detecting and phase correlation can attain 0.08pixel and 0.25pixel respectively.Solar images can be obtained by four telescopes at 13.0nm, 17.1nm, 30.4nm and 19.5nm respectively . It is important for calibration of EUT in orbit selecting a proper spectrum line. Through analyzing and calculating , sensitivity of solar CIII (97.7nm)spectrum line can meet demand of spectrum line for calibration of EUT in orbit. So Solar CIII(97.7nm)spectrum line can be applied to calibration of EUT... |
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