Download TEM Image Mode

TEM Image Mode
The TEM Image Toolbar
NOTE: The TEM Image mode acquires images from a CCD camera connected to the computer via a USB port. Before images can be acquired, the
CCD camera must be mounted to the microscope and connected to computer via the USB cable, and the USB driver and hasp must
be installed. Review and perform the Hardware and Software Installation procedures before proceeding!
TEM Image display and acquisition functions are controlled from the TEM Image Toolbar. If the toolbar is not visible at the top of the computer
screen, selecting Mode → TEM Image from the top menu will make it appear:
The tool bar is divided into four sections:
Image Options. Used to set the image scaling; the menu selections are common to those for SEM Imaging. This section is also used to match
Revolution's magnification to the magnification set at the microscope (the software cannot directly read this information). Refer to the Micron
Marker Preferences for detailed information. This section is also used to specify the beam voltage (informational only, Revolution cannot control
or read the beam voltage from the microscope).
Acquire Image. Used to set or define image resolution for both the acquire and preview modes (they can be set independently). The "camera" and
"eye" buttons initiate acquisition and on-screen preview of the image, respectively.
Tools. Used to select tools for image manipulation. In order from left to right, these are:
Switch to magnify-cursor. Used to zoom in images. Use the option key (Macintosh) or alt
key (Windows) to temporarily zoom out.
Switch to demagnify-cursor. Used to zoom out images. Use
the option key (Macintosh) or alt key (Windows) to temporarily zoom in.
Switch to hand-cursor. Used to drag image around in zoomed mode.
Switch to pointer-cursor. Used for selecting any item with a valid handle in an image.
Switch to text-cursor. Used to create or edit text annotations in an image.
Status. Lists useful information about the current operational state.
Other TEM Image parameters can be controlled via the TEM Image Preferences.
Previewing Images
If no cameras is connected, the status will reflect this fact as shown in
the toolbar at the top of the page. If the hardware has been properly
installed and connected, the status will change to show that the camera
is connected:
To launch a preview window, click on the preview button →
A blank preview window appears on screen and the exposure time
begins, with the corresponding status change.
The film number, beam voltage, and magnification are copied from
the toolbar and inserted below the image, and the date and time are
appended. Also appended are the facility name and user comments,
if they have been entered in the TEM Image Preferences.
When the exposure is done, the image is read from the CCD camera
into the Revolution buffer...
... and then displayed on the computer screen (right).
The image appears on the screen as the data are transferred if Live
Update is turned on in the TEM Image Preferences.
In preview mode, this process is repeated over and over, creating a
live, albeit slowly updating, image.
First Run
When the preview is first displayed on the computer screen, some controls may not be set correctly. Before desirable images can be acquired, two
procedures should be followed. These procedures can be repeated at any time.
Select Resolution
Adjust Brightness and Exposure Time
First Run - Selecting Preview Resolution
Most users will use the full resolution of the CCD camera (1
1 binning) for publication quality images. However, for setup purposes, 4pi
supplies two smaller resolutions, corresponding to 2
2 and 4
4 binning of the CCD's pixels, and also "Selected Area" resolutions.
Click the menu to the left of the preview button to see the available preview resolutions.
2
2 and 4
4 binning is controlled exclusively by the CCD camera and its on-board controller. Each
factor of 2 decrease in resolution results in a proportional (factor of 4) decrease in both exposure time and
data transfer time.
SA = Selected Area. The CCD camera performs a 1
1 binning in the center of the field of view, using a
reduced number of pixels. This procedure is controlled exclusively by the CCD camera and its on-board
controller. Exposure time is not reduced because the binning is still 1
1; however, data transfer time is
reduced proportionally.
First Run - Adjusting the Brightness and Exposure Time
There are no "gain" or "offset" circuits in the CCD interface. Brightness is set by adjusting the TEM condenser lens settings. The exposure time is
set in concert with the brightness. There are no specfic rules other than to make the image look as desired. Exposure times for the CCD camera may
be more or less than the equivalent for film; however, they are unlikely to differ by an order of magnitude. Note: while making this adjustment, the
display setting (toolbar Image Options) should be Full Range.
Acquiring and Saving Images
Select the desired acquisition resolution:
Click the menu to the left of the acquire button to see the available acquisition resolutions.
2
2 and 4
4 binning is accessible as for the preview described above. Each factor of 2 decrease in
resolution results in a proportional (factor of 4) decrease in both exposure time and data transfer time.
Selected Area is not available in acquisition mode.
To start an acquisition, click on the acquire button →
The image will be captured in a separate window. The acquisition may be done while the Preview window is open, or not.
Images (including those that are only partially acquired) can be saved straight to disk at any time by selecting File→Save (keystroke cloverS on Mac, control-S on Windows). The same will work on a preview window.
The default format of a CCD image is selected in the TEM Image Preferences. The data from an acquired image or map can be saved to disk
by keystroke (clover-S on Mac, control-S on Windows), selecting Save from the File menu, or simply selecting the close
box in an acquired window (in a preview window, only File → Save is applicable). The following dialog appears:
The selections available are:
TIFF-Mac. Save the data as a TIFF file in Macintosh
format.
TIFF-PC. Save the data as a TIFF file in Windows
format.
JPEG. Save the image as a JPEG graphic, suitable for
web presentation.
PICT (Macintosh) or BMP (Windows). Save the image
in the native format of the operating system as a picture
that can be pasted into a presentation program.
Flat Field Correction
This correction (or "calibration") step accounts for the imperfections in the light sensitivity of the individual pixel elements within the CCD array.
A full discussion is outside the scope of this document; only the general procedure and a description of the software calculation are outlined here.
The procedure requires that two frames be acquired aside from the desired image: a "dark" (sometimes referred to as "bias") frame, and a "bright"
(sometimes referred to as "flat-field") frame.
The dark frame is taken with the shutter closed; it is a measure of the dark current in the CCD. The bright frame is taken with the shutter open; it is a
measure of the uniformity of illumination. The bright frame should be taken with an illumination close to what will be used for the actual image
acquisition.
The calculation that Revolution
performs is given by the equations:
where Ical is the corrected image, Iraw is the uncorrected image, Ibright is the bright-field image, and Idark is the dark-field image. M is the average
pixel value of the dark-corrected bright field.
To properly perform the flat-field correction, follow these steps:
Remove the sample (recommended), or otherwise adjust the sample so that the TEM viewing screen is uniformly illuminated. To set this
correctly, use the histogram tools (right-click on image, select Adjust Levels) to set the illumination just below saturation.
From the Acquire menu, select Acquire and Save Bright/Dark Fields. This can also be accomplished with the keyboard shortcut clover-D
(Mac) or alt-D (Win). Note that this can be done only at full camera resolution. During the acquisition, This step will save two special files to
disk: Bright Field.mbd and Dark Field.mbd. The files are saved to the top level of Revolution's directory, and are used to perform all flatfield corrections going forward. These files and should not be moved, nor should their names be changed. To create a new correction, repeat
the acquisition of the two frames — the special files will be updated with the new information.
After the flat-field correction files have been created, the Flat Fielding checkbox will be available in the toolbar. When on, the flat-field
correction will be applied to any image as it is being acquired. To temporarily circumvent this, turn the checkbox off.
The flat-field correction can be applied after the fact to any image of full resolution (for example, if the user forgets to turn the Flat Fielding
checkbox back on). To execute this procedure, simply open the image in question and select Analyze → Post Flat Fielding. Once the Post
Flat Fielding has been performed, it cannot be undone (in this case, the user can close the image without saving, and reopen it).
All images that are flat-field corrected will show a "(FF)" notation in the information field below the image.