Focus deviation and focal length discrepancy of the x-ray grid are closely related to the structure of the x-ray grid itself. Lead bars of the convergent x-ray grid are aligned in the direction of focus. The photographic convergence line should coincide with the focus of the line tube, so that the primary ray is parallel to the lead bar and can pass through smoothly, while the direction of the scattering line is random and seldom coincides with the direction of the lead bar. So most of them were absorbed by lead bars, and the image clarity obtained was better. If the focus of the X-ray tube deviates from the convergence line of the filter line, or the filter line is not placed in the prescribed focal length, the loss of the primary ray will inevitably occur. The percentage of the loss is proportional to the magnitude of the deviation and the difference between the focal length and the grating ratio of the x-ray grid. So the filter line should be placed as far as desired. But in practice, some deviations can not be avoided.
Author：X Ray Grids Maker
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Company: Weifang Newheek Electronic Tech Co., Ltd.
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