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The compensation of instabilities in charged-particle beams

机译:带电粒子束不稳定性的补偿

摘要

Instability in the beam 10 of an electron microscope or other high- resolution instrument arises from externally induced periodic noise and lateral drift. The effect of the instability is measured directly in terms of the focal quality of the image while compensating waveforms are superimposed on the instrument supplies and varied to restore the optimum focal quality. Focal quality at a screen 14 is continuously assessed by means of camera 20 and unit 21 which measure the variance of brightness in a succession of images. In response to the value of variance, a programmed computer 23 instructs a power supply unit 24 to produce waveforms of mains and harmonic frequencies and of EHT oscillator frequency, and to follow an iterative routine of steps in magnitude and phase until a desired value of variance is observed. IMAGE
机译:电子显微镜或其他高分辨率仪器的光束10的不稳定性是由外部引起的周期性噪声和横向漂移引起的。不稳定性的影响直接根据图像的聚焦质量进行测量,同时将补偿波形叠加在仪器电源上并进行变化以恢复最佳聚焦质量。借助于摄像机20和单元21连续地评估屏幕14上的焦距质量,所述摄像机20和单元21测量连续图像中的亮度变化。响应于方差值,编程的计算机23指示电源单元24产生电源和谐波频率以及EHT振荡器频率的波形,并遵循幅度和相位的迭代程序,直到期望的方差值。被观察到。 <图像>

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