Lateral x-ray : 4 marks vs 2 marks - PowerPoint PPT Presentation

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Lateral x-ray : 4 marks vs 2 marks

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  1. Lateralx-ray: 4 marks vs 2 marks • Test perfomed using the plate 57 of one brickwith 4 x-ray frontal marks and 4 x-ray lateral marks • The distances between maps in micron are shown in the following slides (as depend on plate position). Legend:- MAP:FXR4 : map evaluated using 4 x-rays frontal marks- MAP:LXR4 : map evaluated using 4 x-rays lateral marks- MAP:LXR2 min/max X side: map evaluated using 2 out of 4 x-rays lateral marks located on the plate side where x is minimum/maximum. (**) (*) A map is a transformation between stage coordinates and nominal (or detector or what.ever.you.want) coordinates (**) The same mark positions of the case with 4 marks are used to not introduce effects due to the mark position accuracy. The map is obtained by simply setting the other marks as NOT FOUND.

  2. MAP:FXR4 – MAP:LXR4 Distance between maps (micron) The rough positions of the marks used are shown in black (1° map) and in white (2° map)

  3. MAP:FXR4 – MAP:LXR2 minX side Distance between maps (micron) The rough positions of the marks used are shown in black (1° map) and in white (2° map)

  4. MAP:FXR4 – MAP:LXR2 maxX side Distance between maps (micron) The rough positions of the marks used are shown in black (1° map) and in white (2° map)

  5. Comments • The distance between MAP:FXR4 – MAP:LXR4 is below 10 micron over the whole emulsion plate • The map evaluated with only 2 lateral marks get worse and the distance can increase up to 50 micron on the opposite side of lateral marks . Let compare the 4-marks frontal x-ray map with a 2-marks frontal x-ray map obtained by simply setting as NOT FOUND the 2 marks with higher x positions … And what happen if we evaluate the distance between this map and the 2 marks lateral x-rays map?

  6. MAP:FXR4 – MAP:FXR2 minX side Distance between maps (micron) The rough positions of the marks used are shown in black (1° map) and in white (2° map)

  7. MAP:FXR2 minX side – MAP:LXR2 minX side Distance between maps (micron) The rough positions of the marks used are shown in black (1° map) and in white (2° map)

  8. Finalcomments • Changingfrom a 4 marksmapto a 2 marksmapintroduceserrors in the position estimation. Thisisalsotrueifyouhave 4 marksmapbutyoudidn’t find 2 marks. • Thisisnotexpectedifyou don’t change the map. Forexamplesifyouuseonly a 2 marksmapfor the entirebrick (i.e. in the scan-back). • Thisis due the differentnumberof free parametersavailablefor the transformation (6 in the case of 3 and more marks, 4 in the case of 2 marks). The scalingof Y coordinatescannotbewellestimatedbymeasutingonly 2 marks (withquite the same Y). • 4-marks lateralmarks are necessaryifyou don’t wanttomanagetheselargeerrors (at the beginningofscanback and at the end of the scanforth or everytimeyouchange the map).