Version 2.1 of TOF_VIS contains the following additions and changes to the version 2.0 ( January 1997 ) release.
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| 1. Q-E Image: Popup display of spectrometer data in Q E space. The data is mapped to form an image in which the X-direction represents E and the Y-direction represents Q. E increases to the right, Q increases downward. |
2. True Angle Image
Popup display of data with Y value proportional to angle. The original TOF_VIS display shows spectra SORTED by angle. However, if there are angular intervals with no detectors, the original display does not show this. The new popup display rebins the data in equal angular steps.
COMMENTS:
The two new popup displays are accessed from the "VIEW" menu using the "ADDITIONAL IMAGE VIEWS" option. When an additional popup view is selected, it's image is loaded from the main TOF_VIS display.
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| The currently selected mode and "TOF", "E", "Q" or "d" range is used for the "True Angle Image". The currently selected "E" range is used for the Q-E image. The Q range of the Q-E image is calculated from the data. | |
To avoid aliasing problems, the popup image is calculated based on the current size of the popup display area. If the popup is resized, aliasing will be introduced. The display can be recalculated if desired by again selecting the display from the "VIEW"..."ADDITIONAL IMAGE VIEWS" menu.
It will also be necessary to reload the popup image in this way when a new data set is read into TOF_VIS.
Most of the controls and features of the popup displays should be familiar. However, in addition to the usual features, the horizontal and vertical cuts in the the popup displays can be averages over a number of rows and columns. The width of the band around the cursor that is averaged is controlled with a valuator labeled "Strip Width". If "Strip Width" is set to 0, only the row or column marked by the cursor is used. If "Strip Width" is set to W>0, the horizontal cut displays the average of rows from row-W to row+W where row is the row containing the cursor. Similarly, the vertical cut displays the average of the columns from col-W to col+W. Finally if strip width is set to -1, the horizontal and vertical cuts become the sum across all rows and across all columns respectively.
At this time, it is assumed that the detector is one inch wide. The range of angles covered by the detector is approximated using that width and the distance to the detector. While this is not strictly correct, it should provide a useful first approximation.
The calculation of the "True Angle Image" is relatively straight forward. However, the calculation of the Q-E image was more trouble-some. Specifically, detectors at negative angles correspond to the same Q values as detectors at the equivalent positive angle. However, since there is not a simple 1-1 correspondence between detectors at positive angles and at negative angles, it would not be correct to just throw all the data together. TOF_VIS has currently adopted the following solution. One Q-E image is calculated for the negative angle detectors and a second Q-E image is calculated for the positive angle detectors. These two images are then combined. If there are non-zero values in both images, the the values are averaged. ( Suggestions as to better ways to do this would be welcome. )
BUG FIXES:
1. A problem the placement of the y-axis title on the hard copy printout has been fixed.
2. A problem with calculating the time interval to use for the initial display of spectrometer data has been fixed.