Image Registration

TODO:

When acquiring surveys and other AugerScan data at high magnification, beam drift can cause the beam to move far from the location of interest. AugerMap can be used to help prevent beam drift by periodically acquiring and SED image, and comparing it to an image acquired just before starting acquisition. If there has been any drift, the beam is then positioned to compensate.

Because image registration uses SED images, you must have a digital multiplier control.

The effectiveness of image registration depends on the quality of the SED image that AugerMap can acquire, as well as the topography of the sample. There must be a feature in the image that is of reasonable contrast for the software to determine spatial movement. It is also important that the feature is not repeated within the image; as in, for example a grid. Because of the way registration works (by comparing “before” and “after” images), you cannot perform registration during a depth profile, because the image will change due to sputtering.

Also, note that image registration can currently only be used when acquiring an AugerScan acquisition in point mode (TV off) in the center of the image. You cannot use it whena acquiring a specific point or area acquisition.

To setup image registration, click the Image Registration command in the System menu. The dialog is described below. There are two aspects to image registration that are controlled from this dialog – setting up the automatic registration during an AugerScan acqusiition, and testing registration on a given image.

Control During AugerScan Acquisition

The following controls govern how image registraion will work during an AugerScan acqusiition.

On/Off

Click the On or Off radio to turn automatic image registration on or off during an AugerScan acquisition.

IMPORTANT: Note that this setting is not saved between AugerMap sessions. By defautl, AugerMap always starts with image registration turned off.

Surveys: Register Number of Sweeps

Type in the number of sweeps between registration. AugerMap will acquire an SED after every multiple of this number of sweeps, and register the image Because image registration takes time (especially to turn the SED multiplier on and off), it will slow down your acquisition somewhat. For very short surveys (a few hundred eV), you may wish to set this to at least a few sweeps, if not more. For longer (1000 eV) surveys, this would normally be set to 1 or 2 sweeps.

Multiplexes: Register Number of Cycles

Type in the number of cycles between registration. AugerMap will acquire an SED after every multiple of this number of sweeps, and register the image Because image registration takes time (especially to turn the SED multiplier on and off), it will slow down your acquisition somewhat. For very short multiplexes (a few regions, with a few sweeps each), setting this to 2 or 3 cycles is probably adequate. Otherwise, once per cycle will produce the best result.

Use Current Reference Image
If you have already acquired a reference image (see below), and are ready to acquire immediately, you can check this box to save some time at the beginning of the acquisition.

Manual Registration

The following controls allow you to determine how well image registration will work under a given set of conditions

Acquire Reference

Click this button to acquire a reference image; one that will be used as the standard to compare all other images against. Once acquired, the image will appear in the reference image dialog box.

Acquire Image

Click this button to acquire an image at whatever location the beam is currently rastering over. Typically, you will have already acquired a reference image, then move the beam (to simulate drift), and click this button. This image will then be compared to the reference image, and the predicted beam shift (X and Y position movement in uM) will be displayed at the bottom of the dialog.

Apply Shift

Click this button to force the comuter to move the beam by the amount displayed to the left. If image registration is working properly, clicking this button should shift the TV image so that it more closely aligns with the reference image