Determining the visual resolution | Slitcamera | Determining the focal spot |
On the resolution measurement and electron-optical adjustment of image intensifier systemsIt is common knowledge that flawless (image or electron) optics cannot exist due to theoretical reasons. The quality of optics reflecting one point in one level of the table, is basically dependent on how well the correction of the following image artefacts has turned out: spherical aberration, chromatic aberration, image field curvature, coma and astigmatism. Especially the last three errors result in:
For this purpose, (at least) 13 test plates are used as far as modern image intensifiers are concerned. One is positioned in the middle of the image and 4 at a time on circles around the middle. Each of the test plates should have line groups in an appropriate resolution range with two line directions that are vertical to each other. Whereas, it is important to note that the actual test field (especially in the spoke direction) is fairly small so that the resolution of certain "points" can be measured. |