EDX image display and acquisition functions are controlled from the EDX Image Toolbar. If the toolbar is not visible at the top of your screen, selecting Mode → EDS Image from the top menu will make it appear:
Before configuring and performing an acquisition that could take hours, one should ascertain that the basic system is configured and operational. The user should verify beforehand that there is no problem either with acquiring an image or a calibrated spectrum. This page will assume knowledge on the part of the user about both of these procedures.
Note: the EDX image capability in 1.6 is significantly different from all previous versions of Revolution. The installer's setup procedure is described below, but the user will rarely need to adjust these settings. In particular, preselecting elements, although it can be done, is not generally necessary as it was in Revolution versions before 1.6.0.
Resolution is set straight from the toolbar:
To configure most settings for EDX imaging, hit the Setup button in the middle of the toolbar to get this window:
Mapping type. Set the mapping type to fast, slow, or slow/live:
Fast. Every pixel is visited for a dwell that set in the Dwell field, in microseconds. This makes mapping "fast" but very few counts (often zero) are collected at every pixel. Frame averaging is required to build up the maps, so the number of frames should be selected accordingly. The acquisition can be stopped at any time, so it is acceptable to just set the frames to an arbitrarily large number and visually decide when the acquisition should end.
Slow. Every pixel is visited once, for the time specified in the Dwell field, in real time milliseconds. Slow mapping implies that only one frame is collected, so it doesn't make sense to turn frames on. This mode is no longer the preferred method of mapping... it takes a long time to determine if the maps contain the needed information, and long dwells can exacerbate beam issues such as charging effects and damage to the sample.
Slow Map (Live). Same as Slow Map (above), but the dwell is based on live time seconds instead of real time seconds.
Frames. Set the number of frames to acquire. See above discussion for advice on this setting: when fast mapping, this should typically be turned on to a high number; when slow mapping, frames should typically be turned off.
Line Sync. Set whether the scan should be synced to the power line frequency or not.
SEM Image Acquisition. Enable as many video channels as desired, and set each of their dwell times and display characteristics, in the same way as described for regular SEM images.
Manual ROIs. Hitting Edit Setup will take you to setup options that in v1.6.0 can be deferred until during or after data are acquired. These configuration options are covered below.
Principle Component. Configures Principle Component Analysis of hyperspectral images.
EDX Pulse Processor. These settings are available only on Universal Spectral Engine systems only. Using the menu, select the desired time constant. In general, shorter time constants are used for mapping; although resolution is poorer, this is usually offset by the faster mapping speeds that can be achieved. The Link checkbox causes the EDX Spectrum functionality to use the same time constant as for mapping.
Press the acquire button (camera icon) to start the acquisition. A container will open and show the selected maps as they are being acquired (example below). The container is fully resizable and is interactive in real time. A full spectrum at every pixel is acquired, as well as the entire chronological history of the acquisition. For this reason, no actual setup other than described above is required: the user can acquire an entire data set, and then select which maps to display after the fact.
|Using the resize box in the lower right corner, the user can resize the container interactively at any time during or after the acquisition:
Tip: using File → Copy, an image of the container can be placed in the clipboard buffer of the operating system, and pasted into another program.
|The user can interact with the maps in real time in the following ways, all by right-clicking in the container and selecting from a variety of contextual menu options:
Operating note: selecting any of these will NOT stop the acquisition. It will continue in the background. When the changes are completed, they will be incorporated into the container as if they had been selected originally.
|There is no need to restart the mapping, even after the mapping is finished!!
Each of the items in the contextual menu is described below.
ROI Processing Context Menu. Opens the ROI Processing window in live interactive fashion, as shown below. Any changes made will automatically update the container when this window is exited. The user can add or subtract elements, change colors, or edit the ROIs. It is not necessary to restart the mapping to incorporate the changes.
To turn on any element, click it to toggle, or right click and select On or Off from the contextual menu. To edit the ROI, right click any element and select Edit Element to get the dialog shown below (the dialog for Copper is shown; default color is always white:
To assign a color to any element, open the computer's color services (not shown) by clicking on Set Color. Choose a color (green in this case) and dismiss the color services dialog.
Optionally, add the L (M) lines to the ROI by clicking on the L (M) checkbox (blue cursor).
The ROI definitions can also be edited in this dialog box. Close the ROI dialog and repeat the process for each element. We selected green for Cu, and cyan for Al.
Color Images. Regardless of the color settings for each element, colors will not actually be shown unless this check box is turned on.
Phase Image. To turn on the Color Phase Map, enable the Phase Image checkbox. The map container will then include a separate composite image of all the maps blended together. Note: Blend Control was dropped in v1.6. The phase image starts with the SEM video but is overwritten by x-ray data. SEM video will persist wherever there are no x-ray counts.
Bkg Subtract. Subtracts background in each ROI. This is not a "true" background calculation as performed in the EDS Spectrum Mode. It is a linear interpolation through the base of the ROI. Note that the subtraction will not make much difference unless there are enough counts in the ROI to make it evident (a condition which is common in mapping).
Show KLM Markers. Superimposes KLM markers in the Edit ROI Processing spectrum window.
Tools. The zoom, drag, and pointer tools all work in either the spectrum or image window in the Edit ROI Processing dialog.
Open/Save/Reset. Open and Save can be used to save or restore sets of element combinations so they do not have to be reentered by hand each time. Reset turns off all elements with one click.
Spatial Frame Lock. When checked, real-time drift correction will be applied to the data cube when the OK button is pressed. To undo the correction, simply reopen the Edit ROI Processing window and uncheck before pressing OK again. Note: if the SFL checkbox is missing, hold the shift key down when pressing OK to turn it on.
When the real-time processing modifications are finished, press the OK button to
return to the real-time container window. The entire data cube will be reprocessed
until it catches up to the in-progress acquisition, and then continue.
Extract [All] Images Context Menu. The images in the container are not the final images that are saved to disk. At any point in the acquisition, the user may extract images in toto or individually. After extraction, all the overlays that were set up for regular images will appear and can be interacted with. While the user is doing this, the acquisition continues in the background. An extracted copper map is shown below as an example. Once extracted, the image can be saved in any of the available formats.
Image Color Context Menu. Shortcut to change the map color. If color change is all that is needed, use this instead of reopening the ROI Process window.
Adjust Levels Context Menu. Opens the histogram tool to give the user real-time interactive control over the brightness and contrast of any map or image. The changes are reflected interactively in either the container or an extracted image:
Show Line Plot, Edit Comments, Edit Magnification Context Menu. These items are available only in extracted images, and allow the user to interact with the graphics layers in the images in the normal fashion.
At any time during a map acquisition (or after), spectra can be extracted from any set of pixels in a map container. The spectra will appear in new live windows that can be operated on independently, all while the acquisition of data continues. From the toolbar, select any of the extraction geometries (point, line, rectangle, polygon) and place them in any map or image in the container. Points are a single click. Lines and rectangles are click-and-drag. Polygons are multiple clicks, one at each vertex, and a final double-click to close the shape:
After any particular tool shape is placed in the container, right click on that shape and select Extract Spectrum:
The extracted spectrum will appear with a reminder image that can be moved or resized:
To quant the spectrum, right-click anywhere in the window and select Quantify:
The final result is an independent window with a quanted spectrum from only that selected area:
The number of spectrum windows that can be extracted in this fashion is unlimited. Each will be an autonomous live window that continues to acquire data and can be manipulated independently of all other extractions and the container; however, all extracted windows will be linked to their particular container. New containers, all with their own set of linked autonomous live extracted windows, can of course be opened as well.
Either by clicking on the container-window close box or selecting File→Save, the standard save dialog window will appear; two saving choices are available:
|Flatten Frames (the default) will compress all time history out of the event file. Subsequent reopening will include the full 3-D data cube, but not the history; therefore, no further Spatial Frame Locking is possible in such a file.
All Frames will save the entire event stream to disk, allowing a complete replay of the acquisition, frame by frame. In this mode, Spatial Frame Lock can be toggled on and off.
Note: As a basic rule of thumb, flattened files will occupy 4-5 times less disk space than entire event files.
The most common complaint about acquired x-ray maps is "nothing was acquired; the map is black." This is invariably because the physics of the acquisition process has not been considered. As an example, consider an output count rate of 2000/sec. This is counts into the entire spectrum. If the spectrum consists of 2000 channels, this is an average of one count per second per channel. A typical spectrum might have most of the counts concentrated in 5 ROIs, so there are perhaps 400 counts/sec going into each ROI. A dwell time of 10 millisec per pixel then yields, on average, 4 counts per ROI per pixel when the map is finished. When autoscaling, this is enough to create a visible map; however, if the map is not autoscaled, or if the count rate or dwell is not large enough, the maps will be black. Always do a back-of-the-envelope calculation to see if your acquisition conditions make sense!!
The dwell time operating note is even more important in the case of fast mapping, because the mapping is proceeding at the scan rate for SEM imaging (typically 1000 times faster). As a result, there are usually no x-ray counts to be recorded at any particular pixel. In this case, the dwell should be set to either 2 or 3 times the pulse processor time constant. Furthermore, since frame averaging is usually used with fast mapping, the dwell times for the video images can be set to a small value. If allowed by your measurement environment, we also suggest adjusting spot size and/or aperture to significantly increase the count rate (40-50% deadtime is not unreasonable).