Navigator menu commands

The Navigator menu has commands for opening the Navigator window, operating on Navigator files, and performing less common Navigator operations.

Open Open the Navigator window.
Read & Open Read a Navigator file and open Navigator window if it is not open.
Merge File Merge items from other Navigator file into current items, eliminating duplicates.
Save Save current Navigator items to a file.
Save As Save current Navigator items to a different file.
Close Close the Navigator window.
Montaging & Grids This submenu has operations for setting up montages, super montages, and grids of points.
   Setup Corner Montage Define a montage that captures area inside corner points.
   Setup Polygon Montage Define a montage that captures area inside a polygon.
   Setup Full Montage Define a montage to capture the full grid area.
   Set Grid Limits Set limits in X and Y for the full-grid montage.
   Setup Super Montage Add polygons representing overlapping montages aligned to camera axes.
   Polygon Super Montage Add polygons representing overlapping montages to fill the current polygon
   Add Grid of Points Add a set of points on a regular grid either filling a polygon or in a full rectangle.
   Divide Point into Groups Place points in groups with a maximum radius from first point at the center.
   Set Group Size Set the maximum radius for groups of added points.
   Set Multi-shot Parameters Set parameters for acquiring multiple Records in a hole with image shift.
   Show Shots when Show Acquire Show a pattern of beam circles for the multiple Records when Show Acquire area is turned on.
   Add Circle Polygon Add a polygon that is a circle of specified radius.
   Polygon from Corners Make a polygon from the current set of corner points.
Options The submenu has various options to control autosaving, file type, map loading behavior, and drawing of point labels.
   Set Point Label Threshold Set maximum size of group for which point labels will be drawn.
   Autosave Nav File Periodically save entries to file.
   Write as XML Write Navigator file as an XML file instead of in autodoc format.
   Convert Maps to Bytes Convert maps to bytes when creating or loading them to save memory.
   Load Maps Unbinned Always load maps with overview binning of 1.
   Use Current LD Params in Realign When staying in Low Dose for Realign to Item, use current instead of map parameters.
Transform Points Transform items to the current registration.
Undo Transformation Undo the last transformation between registrations.
Change Registration Change registration of current item.
Shift to Marker Shift items by distance from current item to marker point.
Undo Last Shift Undo the last shift to marker point.
Align with Rotation Align image to map taken before rotating specimen.
New Map from Image Make a new map from the current image.
Import Map Define an externally acquired image as a map.
Rotate Map Rotate a map to correct orientation at current registration and magnification.
Adjust for Backlash Adjust stage position of map so that it can be returned to with backlash correction.
Backlash Settings Open dialog to control when program will adjust a new map for backlash.
Open State Dialog Open dialog for saving and setting imaging states
Set Map Acquire State Set mag, beam, and Record parameters from current map
Restore State Restore mag, beam, and Record parameters from setting to map state
Acquire at Points Acquire images or maps or run a tilt series or script at a sequence of areas automatically.
End Acquire Stop automatic acquisition after item being worked on.
List Files/Series/States List the tilt series to run, files to open, or states to set during an acquire
Delete Item Delete the current item or group of items.
Realign to item Use correlation to map(s) to center on the current item.
Force Center Align Make Realign to Item align to center of map even if it has recently aligned to it.
Try Scaling in Realign Find image scaling in first round of Realign to Item to adjust for shrinkage

Open command (Navigator menu)

Use this command to open the Navigator window.

Read & Open command (Navigator menu)

Use this command to read in a Navigator file as well as open the window if it is not already open. The file will become the current file for saving into.

Merge File command (Navigator menu)

Use this command to read in the items from another Navigator file and merge them in with the items currently present in the table.  Duplicate items will be eliminated.  If an item has a label that matches that of an existing item, it will be changed by adding '-1' to it (or '-2' if the label with '-1' on it exists, etc.).

Save command (Navigator menu)

Use this command to save Navigator items to a file. The file is a simple tab-delimited text file with the properties of each item. If there is no current Navigator file, you will enter the Save As dialog box to specify the file, which will have the default extension .nav. When you select this command again, the entries will be saved to this file.

Save As command (Navigator menu)

Use this command to save Navigator items to a file different from the current file. You will enter the Save As dialog box to specify the file. The new file will become the current file for saving into.

Close command (Navigator menu)

Use this command to close the Navigator window. If the contents of the window have changed since it was last saved, you will be asked if you want to save them to a file.

Set Point Label Threshold command (Navigator - Options submenu)

Use this command to set a threshold for skipping the drawing of most labels on points when they belong to groups bigger than the threshold.  Enter the maximum group size for which all labels should appear, or 0 to draw labels regardless of group size.  The labels of the first and last points in the group will be drawn in groups bigger than the threshold. Also, the labels of up to five points around the currently selected point will still be drawn even if the selected point is in a group larger than the threshold.  Labels will also be drawn for points whose distance from the previous point is greater than 40 microns.

Autosave Nav File command (Navigator - Options submenu)

Toggle this menu item on to have the Navigator items saved to a file periodically if they have changed. If there is no currently open file, the program will save to a file named AUTOSAVEmmddhhmm.nav, where 'mmddhhmm' are two-digit values for month, day, hour, and minute. This file will be removed when you save to a file or when the program exits (if you elect not to save at that time). However, if the program crashes, you should find the file in the directory in which your SerialEM shortcut starts the program.

Write as XML command (Navigator - Options submenu)

This command toggles an option to save the Navigator file as an XML file instead of in autodoc format.  Either one can be read back in by SerialEM.  The autodoc writing is significantly faster because it is optimized to write each line directly to file, whereas to write an the XML file the program builds an autodoc data structure, builds an XML structure from that, then writes out the XML.  This will matter only for very large numbers of points, over 10,000.

Convert Maps to Bytes command (Navigator - Options submenu)

This command toggles an option to keep maps in memory as bytes. The option does not affect how maps are stored in the image file (typically as integers). Byte conversion will reduce memory usage by 2/3, so that the memory required is just one byte per pixel. The intensity scaling determined by the Black and White levels in the Image Display control panel will be associated with an image when a new map is created. This scaling is then applied to convert the image to bytes, both when the map is defined and when the map is reloaded from file. This scaling could make it impossible to see some light or dark image details. There are two ways to prevent such scaling problems. First, adjust the Black and White levels to avoid truncating image intensities before designating an image as a map. Second, use this menu entry to turn off the conversion option, load the map, adjust the Black and White levels as desired, and turn the option back on.  This option is not saved in the settings file between sessions; it can be turned off by default with the general property 'ConvertMapsToBytesDefault 0'.

Load Maps Unbinned command (Navigator - Options submenu)

This command toggles an option to have montage maps always loaded unbinned, i.e., with overview binning of 1. This is almost always what one wants, but if you are short on memory and do not need to see a map at full resolution, you can turn off the option and set a higher overview binning in the Montage Control panel . However, if the map file is open, you must make it the current open file before setting the binning in the control panel.

Use Current LD Params in Realign command (Navigator - Options submenu)

This command toggles an option to use the current Low Dose parameters for Realign to Item instead of the Low Dose parameters set when the map was acquired.  The option applies only when staying in Low Dose mode for the Realign operation, which occurs as long as the current camera, magnification, and probe mode (on an FEI scope) or alpha (on a JEOL) match the map condition.  By default, the Realign operation imposes the map conditions when realigning to a map.  This option is available because there are situations where it is advantageous to take the map under different conditions.  For example, more dose might be desired for the map to allow either better visualization of features or more reliable montage piece alignment, while less dose can be used for correlating with those maps.

Setup Corner Montage command (Navigator - Montaging & Grids sub-menu)

Use this command to set up a montage to capture the area within the current set of corner points. Be sure to go to the desired magnification before activating this command. You will be opening a new image file for the montage, so if there is already a file open the program will ask whether you want to close it. The program will compute the number of montage frames in X and Y required to capture the area, and decide whether the montage should be acquired with image shift or stage movements. If the area of the Record parameter set is substantially smaller than the camera field, you will be asked whether you want the frame size to be kept smaller than the current Record area. You might want this if the beam is too small to fill the whole camera field. Otherwise, the program will make the frames as large as possible. Unless there are too many frames, you will then go on to the Montage Setup dialog box, in which you will see the number of frames and their size and overlap. If the size of the montage is not reasonable (e.g., bigger than 10K by 10K pixels), you can change the magnification to adjust the number of frames and achieve the desired image size. You can also adjust the percentage overlap, which may also change the number of frames needed to fit the desired area. Once you have set up a reasonable montage, go on to the File Properties dialog box then the Save As dialog box.

After the montage is defined, the program will compose a list of pieces that are not needed to capture the intended area. These pieces will be excluded when the montage is acquired.

Setup Polygon Montage command (Navigator - Montaging & Grids sub-menu)

If the current Navigator item is a polygon, use this command to set up a montage to capture the area within the polygon. It works the same as the Setup Corner Montage command .  Once the montage is set up to capture an area of a particular shape, it can be used to capture the same area at other locations without drawing a new polygon.

Setup Full Montage command (Navigator - Montaging & Grids sub-menu)

Use this command to set up a montage to capture the whole grid area. A set of points will be composed that contain the grid area. The command then works the same the Setup Corner Montage command .

Set Grid Limits command (Navigator - Montaging & Grids sub-menu)

Use this command to enter lower and upper limits in X and Y for the full grid montage. A dialog box will come up for each limit; enter the desired limit in microns or 0 to use the default limit that is shown.  These defaults may be set with the 'StageLimits' property in the SerialEMproperties.txt file to prevent the stage from moving beyond a usable range. If you enter a number bigger than one of the defaults, you may get farther out to the corners of the usable area, but the stage will still not be moved beyond that limit.  If you want access to the full range of motion on a JEOL scope, you need to enter or change the 'StageLimits' property to be '-1190 1190 -1190 1190' (or less extreme values if appropriate).

Setup Super Montage command (Navigator - Montaging & Grids sub-menu)

Use this command to add a set of rectangles at the positions of overlapping montages, laid out on a rectangular grid that is aligned to the camera axes. First, you must have montaging set up with the desired number of pieces and magnification. Specify a center position in the active image by clicking with the left mouse button. Then select this command. You will be asked to enter the number of montages in X and in Y then the number of pixels of overlap in X and Y. A set of polygons will be created, numbered by their positions in the super montage. To try again with different parameters, just use the Delete button in the Navigator to delete the whole group of items.

To get fairly accurate overlaps between montages, use the following procedure. First take a montage that encompasses the whole needed area, at a lower magnification if necessary. On an FEI microscope, it is recommended that you use the option to realign with image shift (see Acquiring High-Quality Montages of Large Areas in Montaging and the last paragraph of Returning to a Position Reliably in Using the Navigator for details). Turn on 'Align pieces in Overview', and also have 'Sloppy montage' on as well if this is needed to get the pieces properly aligned. Make this montage be a map. Then go to the working magnification for the supermontage and set up the montage file. After you answer the queries about number of montages and overlaps, you will be asked if you want the positions to be laid out at regularly spaced image positions rather than stage positions. Do not select this option unless the pieces are indeed properly aligned in the area covered by the supermontage (there can be errors in alignment elsewhere). Also, only select this option if you are going to use the 'Realign to Item' routine at some point to get to individual montage positions. One approach would be to check 'Acquire' for each of the new montage position items and then run the Acquire at Points command with the option checked to 'Realign at item'. This will yield montages that can be blended and analyzed for overlap.

The Setup Super Montage command was originally called Aligned Super Montage, and there was also a Skewed Super Montage command to lay out montages on a grid that is aligned to the specimen axes. Such montages require more overlap to avoid gaps between montages, and the stitching programs in IMOD work well with the aligned supermontages, so the skew capability has no apparent merit.

Polygon Super Montage command (Navigator - Montaging & Grids sub-menu)

Use this command to add a set of rectangles at the positions of overlapping montages that will fill a polygon. First, you must have montaging set up with the desired number of pieces and magnification, and the current Navigator item must be a polygon. After you select this command, specify whether the positions should be marked for acquisition. The supermontage will include any montage that is needed to cover the area within the polygon, with a little allowance for errors in positioning. You can then use the 'Skip pieces outside Navigator item' option in the Montage Setup dialog box, to have each individual montage include only the frames inside the polygon. If you use an entry of 0 there to specify the current Navigator item, be sure to reselect the polygon item after defining the supermontage.

Add Grid of Points command (Navigator - Montaging & Grids sub-menu)

Use this command to add a set of points on a regular rectangular lattice. Four different kinds of grids can be defined: points in a rectangle; points on a defined rectangular lattice to fill a polygon or map; points along a line, and points at a defined spacing to fill a polygon or map. For the first two kinds, the position of the lattice is specified by a group of 5 points, three at corners of a rectangle and two more adjacent to one of the corners. Here, holes that should be marked with a point are shown with 'X' and the rest of the holes are shown with 'o'.

X      o      o      o      o

o      o      o      o      o

o      o      o      o      o

o      o      o      o      o

X      o      o      o      o

X      X      o      o      X

To make all of the points be in one group, press the 'Add points' button and mark all 5 points before pressing 'Stop Adding'. As long as one of the points is the current item, you can select this command. The program will then ask for the label of a polygon that you want to fill. If you leave the text box blank, it will create points for all positions in the rectangle indicated by the corners. If you enter a valid label for a polygon that contains the points (specifically, the centroid of the points), then it will add points to fill the polygon, extending the rectangle beyond the corners that you have marked if necessary.  If you are filling an elongated region, you can reduce errors from extrapolation by marking the corner with two adjacent points near the middle of the region instead of near one end.

Once you have added a grid with a 5-point pattern like this, you can add a grid in a new area with the same spacing and orientation by simply adding a single point in the new area.  It must be the only point in the group, so press 'Add points', add the point, and press 'Stop Adding'.  If you are not filling a polygon, the point should be at the same corner of the region to fill as the corner of the 5-point pattern with two adjacent points.  If you are filling a polygon, put the point near the middle of the polygon to reduce extrapolation errors.

To add a line of points, simply add a group of three points to indicate the extent and spacing of the line, such as:

X    X    o    o    o    o    o    o    X

As long as one of these points is the current item, the command will be available and will add a line of points between the endpoints.

Finally, to add equally spaced points within a polygon or map but not on a defined lattice, simply make the polygon or map be the current item and select this command. Then enter the desired spacing in microns.

When adding points to fill a polygon or the rectangle of a map, the points will not be placed right up against the border of the polygon. Rather, a square box around each point is required to be fully within the polygon. The size of this box as a fraction of the spacing between points is controlled by the GridInPolygonBoxFraction property, whose default value is 0.75.

Grid points can be added in two different patterns. One is a zigzag pattern, which was the only pattern in SerialEM version 2.x, and was designed to minimize stage movement when moving between points. The other pattern goes in the same direction in each row and column, and proceeds in an overall direction away from the location of the Focus area in Low Dose mode. This pattern ensures that focusing is done in areas that have already been acquired from.  However, this pattern is not used when added points are placed into separate groups.

Divide Points into Groups command (Navigator - Montaging & Grids sub-menu)

When this option is selected, the set of points added with the Add Grid of Points command will be divided into multiple groups.  The middle point of the group will be the first point, and its distance to every other point in the group will be less than the maximum radius set with the Set Group Radius command.  With this arrangement, you can use the option in the Acquire at Points dialog to focus only on the first point in a group, and other points will be within a certain distance of the location where focus was last done.

When points are divided into groups, the program will display the result, tell you the number of groups and points per group, and ask if you want to keep this grouping.  If groups are too large or small, just press No and all the points will be removed.

Set Group Radius command (Navigator - Montaging & Grids sub-menu)

Use this command to set the maximum radius used for dividing points into groups as described above.  Sometimes groups will be smaller than they could be for a particular radius, because the total extent in each direction of the grid gets divided into groups as evenly as possible.

Set Multi-shot Parameters command (Navigator - Montaging & Grids sub-menu)

Use this command to open the Multiple Record Setup dialog and set parameters for taking multiple Record images in a circular pattern around the current position.

Show Shots when Show Acquire command (Navigator - Montaging & Grids sub-menu)

This command toggles whether selecting the 'Show Acquire area' checkbox in the Navigator window will also result in a pattern of circles drawn around the marker point, based on the parameters set in the Multiple Record Setup dialog.  The circles will represent the area covered by the beam, assuming the beam size specified there.

Add Circle Polygon command (Navigator - Montaging & Grids sub-menu)

Use this command to add a polygon that is a circle. First mark the desired center point by clicking in an image. Then select this command and enter the desired radius in microns.

Polygon from Corners command (Navigator - Montaging & Grids sub-menu)

Use this command to make a polygon from the current set of points marked as corners.  After the polygon is made, you will be asked whether you want to delete all of the corner points. If you answer No, they will be retained but no longer be marked as corners.  With this command, you can use corner points to define one polygon after another, and then set up each polygon for automatic acquisition into a different montage file.

Transform Points command (Navigator menu)

Use this command to transform items from one or more other registrations to the current registration. The program will find a transformation whose complexity depends on the number of registration points available. Just a shift will be found with 1 point, a rotation and shift with 2 points, rotation, scaling, and shift with 3 or 4 points, or a full linear transformation including stretching with 5 points. All items except the registration points will then be transformed and associated with the current registration. The program will give a message about how well the points fit the transformation equation. If the fit is very poor, you can undo the transformation with the command described next, fix the problem, and redo this command.

If stretch in the stage coordinate system has been calibrated with the Stage Stretch command , then transformations based on 2 - 4 points will incorporate this stretch, and the report on the transformation in the log will include the text '(corrected for stage stretch)'. When transforming after a large specimen rotation, such transformations may not be very accurate in the absence of such a calibration, but the calibration allows reliable transformations with only two or three points.

Undo Transformation command (Navigator menu)

Use this command to undo the last transformation done with the Transform Points command . Each item will be returned to its former registration, even if items were transformed from more than one registration. This is the only way to undo a transformation of imported items.

Change Registration command (Navigator menu)

Use this command to change the registration of an existing item without changing the current registration. This is different from changing the registration point number, and in fact the command cannot be applied to registration points. If you need to change the registration of a registration point, turn off its the 'Registration point' button before changing the registration.

Shift to Marker command (Navigator menu)

This command provides a simple method of shifting items without having to make registration points. One way to use it is to add a single point at a recognizable feature on an existing map. Then take a new image, click on the feature with the left mouse button, select this command. You will be told what the shift is and asked to confirm the shift. All items at the registration of the image that was clicked on (typically the current registration) will be shifted by the same amount. Another way to use this command is to run the Realign to Item command on a map or an item located in a map. When the procedure is done, take an image, click in the center of it, and select this command. Items will be shifted by error in stage position found in the procedure. Finally, the command can be used to shift registration points to fit imported items. Suppose you import a map, work out registration points, transform the map, and then import another map that is shifted in position. Then select one of the registration points, click on the corresponding point on the new imported map, and select this command. The registration points will be shifted but the map will not, so the points should appear at the right place in this map. This map can then be transformed into registration with EM maps.

Undo Last Shift command (Navigator menu)

Use this command to undo the shift imposed by the 'Shift to Marker' command. It is disabled if the 'Transform Points' command is used.

Align with Rotation command (Navigator menu)

This command opens the Align with Rotation dialog box , which allows you to align a current image with a map taken prior to rotating the specimen. You can also use this alignment to transform items into the new registration, although this transformation is of limited accuracy at long distances from the point being aligned. In order to open this dialog, the map must be in the buffer that images are read into (i.e., just load the map), and there must be an image in buffer A at a different registration from that of the map. Thus, after rotating the specimen, increase the current registration in the Navigator, then take an image at the same magnification as the map.

New Map from Image command (Navigator menu)

Use this command to define the current image as a map. It performs the same operation as the New Map button in the Navigator dialog; see the help for New Map for a full description.

Import Map command (Navigator menu)

Use this command to define an image obtained elsewhere, such as on a light microscope, as a map. First, a dialog will open to allow you to select the file. You can select TIFF and DigitalMicrograph files (dm3 or dm4 type) as well as MRC files, and you can use color images. Then the Navigator Import dialog box will open to allow you to specify the section number, a stage position, a registration number, and a transformation between stage and image coordinates. If you import a TIFF file, the stage position and the stage to image transformation may be automatically selected if there are tags in the file defined in the SerialEMproperties.txt file. The dialog will also allow you to make a color overlay of the selected file and the currently selected Navigator item, if the latter is an imported map of the same size. Imported maps are originally forced to have a registration number separate from those of non-imported items, so points marked on imported maps will not appear on other images, and vice-versa. However, once you transform the imported map into the same registration as the other images, then points marked on the imported map will appear on other images and can be used to move the stage to a desired location.

When points are marked on a map, the program stores the ID of the map that they were drawn on.  This "drawn on" ID is used to help decide what map to use for the Realign to Item routine, but an imported map cannot be used in that routine.  When the imported map is transformed into registration with another map, the "drawn on" ID of any non-registration points marked on the imported map will be switched to the ID of the map that was registered to, and any points added after the transformation will also be given that "drawn on" ID.  Thus, that map will be preferred for realigning to.  In order for this to occur, all the registration points must be picked on just the two maps, one imported one and one native one being aligned to.

Rotate Map command (Navigator menu)

Use this command to rotate the map in the active buffer into the correct orientation for the current magnification and registration, or to rotate an imported map by a desired angle. Specifically, the rotation may include two components: the relative rotation between the magnification at which the map was acquired and the current magnification; and whatever rotation and mirroring around the X axis resulted from any transformations that have been applied to the map item. Points will still display correctly on the rotated map, and new positions can be marked on it. A map can be rotated more than once, or it can be reloaded and rotated to a new orientation.

If a map is imported and has not yet been transformed into registration with native EM maps, then the program will ask you the angle by which to rotate the map (counterclockwise is positive).

Adjust for Backlash command (Navigator menu)

With this command, the program will measure the stage backlash at the location of the current item and then adjust the item's stage position and record the backlash direction used.  When stage backlash is substantial, this can improve the accuracy of returning to that location.  The measurement involves dropping magnification if necessary, or going to the View area in Low Dose mode, taking an image, then moving away and back by the backlash amount, taking a new image, and aligning it.  The stage position of the item will be adjusted by the alignment shift.  The backlash used is the same as the backlash for a montage at the starting magnification.  The command is available only for an item with a directly measured stage position (i.e., a map, or point created with Add Stage Pos), and only if the stage is still at the original position.

Note that whenever a map has a backlash recorded for it, the program will correct for backlash in the corresponding way when moving to a point marked on the map.  Montages made with stage movement automatically have a backlash recorded, but other maps may require this backlash adjustment, unless they were taken at a location where the stage was in a known state with respect to backlash.

Backlash Settings command (Navigator menu)

Use this command to open a dialog box for settings that control whether the backlash adjustment routine described just above will be run when a new map is added.  The dialog has a text box for specifying the minimum size of map for which the program should even consider running the routine.  There are three choices:

  1. Do not run the adjustment routine automatically or ask whether it should be run.
  2. Ask whether the adjustment routine should be run when making a new map larger than the minimum size.
  3. Run the adjustment routine automatically when making a new map larger than the minimum size.

When you use the Anchor Map function, the program will automatically adjust for backlash, if necessary, unless you have chosen option 1.  The higher magnification item that you are anchoring will also have its position adjusted, provided that the stage is still at the same location.

Open State Dialog command (Navigator menu)

Use this command to open the Imaging State dialog box , which can be used to store and set different states for image acquisition. Because the ability to manipulate microscope and imaging state is particularly helpful when using the Navigator, this dialog will open automatically along with the Navigator if it was open the last time that the Navigator was open. If you close the dialog before the Navigator, however, you need to use this command to reopen it. You can also use this command to open the dialog without opening the Navigator.

Set Map Acquire State command (Navigator menu)

Use this command to return to the conditions under which the currently selected map item was acquired, to facilitate acquiring another map in the same state. The microscope state includes magnification, intensity, spot size, and energy filter settings. The camera acquisition state includes the binning, exposure time, and drift settling of the Record parameter set. Low dose will be turned off if it is on. If the file containing the selected map is still open in SerialEM, it will be made the current file. If the file is not open, it will be reopened so that a new map can be saved into it. This command performs the same operation as the Set Map Acquire State button in the Imaging State dialog box.

Restore State command (Navigator menu)

This command will restore the microscope and camera acquisition state that was present before the last time that 'Set Map Acquire State' was run, or before the imaging state was set from the Imaging State dialog box. If a file was opened when 'set Map Acquire State' was run, that file will be closed again. If the file that was current at that time is still open, it will be made the current file again. Low dose mode will be restored to its state prior to the state changes. This command does the same thing as the Restore Prior State button in the Imaging State dialog box.

Acquire at Points command (Navigator menu)

Use this command to acquire images or maps or run a script or tilt series at a series of points marked for acquisition with the 'Acquire' or 'Tilt series' check box in the Navigator window. There must be an image file open before the command can be used to acquire images or maps, unless 'New file at item' has been set for the first item to be acquired. If montaging is to be used, this means that the montaging must be set up already. Be sure to have magnification, intensity, and exposure times set before starting the acquisition, unless an imaging state has been set for the first item. This command opens the Navigator Acquire dialog box, which allows various options to be set.

End Acquire command (Navigator menu)

After starting an 'Acquire at Points', use this command to stop the Navigator from going on to the next item after finishing the current one.  If the acquisition is already paused after finishing an item, the command will stop acquisition immediately.

List Files/Series/States command (Navigator menu)

Use this command to get a list in the Log window of everything that has been scheduled to happen in the course of running an 'Acquire at Points' operation. Specifically, the list will show the files that will be opened and their properties, the imaging states to be set when files are opened, and the tilt series that are set up to run.

Delete Item command (Navigator menu)

Use this command to delete the current item from the list, or to delete the group of items summarized on the current line of the table if 'Collapse groups' is on. A group is created whenever a set of items are added in single operation: i.e., when adding a series of points by clicking on an image, when defining a supermontage, or when adding a grid of points. If the current table line summarizes a group, a message box will appear telling you how many items will be deleted and the range of their labels, and asking you to confirm the deletion.

Realign to Item command (Navigator menu)

This command can be used to return accurately to the position of an item by correlating with available map images. The item must be located within, or must itself be, a map whose extent is large enough to allow the position to be found reliably. Specifically, the map must be at least 3 microns in extent (or more, if the property file specifies a larger limit). Maps taken in LM mode will not be used for these correlations unless they are from a relatively high magnification in LM where images can be taken with the objective aperture in. There are basically three different situations in which this procedure can be used:

  1. The item is not a map, just a point or polygon. It must be located within a big enough map, but it can be very near the edge of the map. In this case, the program will first move the stage to the center of the map, or to the center of one frame of the map if it is a montage, then take an image and align it to determine the error in stage position. It will then move the stage to the position of the item, take a new image, and align it to work out the error from that small stage movement.
  2. The item is a map that is not located in a larger map, so it must itself be large enough for reliable localization. The program proceeds as just described, except that it ends up aligned to the center of the map.
  3. The item is a map located within a significantly larger map. In this case, the larger map must be the minimum required size, but the item being aligned to can be small. The program proceeds as above to find the item position by correlating with the larger map. Then it raises the magnification to that of the item itself, takes a new picture, and aligns it with the map item using image shift. This image shift should be relatively small provided that the position was found accurately at the lower magnification, and that the calibration of image shift offsets between magnifications is still accurate.

When a map is defined, the program stores the brightness, spot size, and exposure settings used to take the map images, as well as the state of the energy filter if appropriate, and these settings are used in this routine to take the images for correlation. The beam size and centering must be robust enough to work at the different magnifications. In other words, if the beam shifts between the different magnifications, it must be spread enough at one of the magnifications so that it still covers the field without being centered.

The previous state of the microscope is restored after the procedure when it is run with this command from the menu or the corresponding button in the Navigator window. When it is run from a script, the state may or may not be restored depending on what is specified in the script command.  However, when the routine is called while in Low Dose mode, the state is always restored by going back to the previous Low Dose area after taking images in the same conditions as the map.

In most cases, the routine will adjust for misalignments between magnifications even if you have not selected the 'Adjust image shift between mags' option in the Alignment & Focus control panel. Specifically, in situations 1) and 2) above, if the microscope state is being restored after the routine runs, then the feature being aligned to should appear centered at the restored magnification. In situation 3, the feature will be centered at the magnification of the map item being aligned to.

Force Center Align (Navigator menu)  

This command makes the Realign to Item routine forget previous information about a recent alignment to the center of the map and do the first round of alignment to the map center.  By default, Realign to Item will skip that first round if the same map was aligned to recently and the alignment error was low enough.  If the first round fails, it may be necessary to use this command to prevent the skipping on the next attempt.

Try Scaling in Realign (Navigator menu)

This command toggles an option to try to adjust for specimen shrinkage when doing Realign to Item .  On the first round of the realignment, where an image is aligned to the center of a map frame, the program will search for the image scaling that makes it align best to the map frame.  This scaling is then used to adjust the target position (which is not at the center) for the shrinkage that occurs.  The scaling will not be done if the program is in Low Dose mode prior to the Realign operation.