求翻译：由于SEM的放大倍数由显像管的幅度和试样表面扫描线度之比决定它可以在20万倍到50万倍之间连续调节(低端要与普通光学显微镜放大倍数衔接)。SEM没有成像透镜，不存在聚焦平面的问题，所以景深长，视野大，图像清晰，富于立体感，可直接观察各种表面凹凸不平的细微结构。是什么意思？

Since SEM magnification ratio is determined by the magnitude of the tube and the sample surface scanning line degrees which can be continuously adjusted (low to ordinary optical microscope magnification adapter ) between 20 times to 50 times .

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Because the SEM enlargement factor by the teletron scope and ratio of the test specimen surface scanning dimension decided it may adjust the low end in 200,000 times to 500,000 times( between to want and the ordinary light microscope enlargement factor engagement continuously).SEM does not have the

Because of SEM magnification by scanning lines of the picture tubes and sample surface than the decision it can be continuously adjusted between 200,000 times to 500,000 times times (low-end to dovetail with the ordinary optical microscope magnification). SEM no Imaging lens, focus plane is not an i

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