Calibrating the camera length

The Camera Length calibration process is required when calibrating images in Diffraction mode.

Use the Camera Length calibration process to acquire correctly calibrated images. Correctly calibrated images are a necessary precondition for being able to measure, for example, distances and angles on your images.

The Camera Length calibration process can only be carried out in Diffraction mode.

Calibrating the camera length

Prerequisites:

•You need a calibration standard to perform the calibration process. You can use an aluminum or a silicon standard, for example.

•The microscope is in Diffraction mode.

Setting up your microscope

1.Put your calibration standard into your microscope. For example, use an aluminum standard.

2.Make the necessary microscope settings and make sure that a diffraction image is displayed.

Preparing image acquisition

3.Switch to the Acquisition layout. To do so, select the View > Layout > Acquisition command.

•In this layout, all tool windows that you need for the image acquisition are automatically displayed.

4.In your software, make sure that the calibration standard is optimally displayed on the monitor.

•Switch to your camera's live mode. To do so, use the Acquire > Live command.

•In the Camera Control tool window, choose an automatic exposure time.

•Adjust the electron beam intensity.

Performing the calibration process

5.Start the Camera Length calibration process. To do so, select the Camera Length entry in the Acquire > Calibrations dialog box. Then click the Calibrate... button.

6.The Calibrate Camera Lengths dialog box opens.

7.If you've already carried out the Camera Length calibration process once, the Calibrated camera lengths group will already contain calibration data. In this case, delete all existing calibration data.

8.The Procedure group describes the calibration process flow. In the list under step 1, you can find a list with all supported calibration standards.

6.In the Procedure group, select a calibration standard. Select the Aluminium (polycrystal) entry for polycrystalline samples or Silicon (single crystal) for monocrystalline samples, for example.

7.In the Miller Indices picklist, select the Miller Indices for which you want to measure the spots.

8.Select the Calibrate on live image check box.

9.Select the Use Snap to brightest pixel function check box if you want the calibration reference distance's reference points to automatically snap to a diffraction reflex near the position that is clicked.

10.Click the Set Calibration Distance... button.

•Your software will automatically switch to the live mode.

•All software functions for the image acquisition are now available.

11.Select a camera length that allows an optimal display of the pair of spots or the diffraction ring.

12.Check the image acquisition settings.

13.Bring the diffraction image into focus.

Setting the calibration distance

14.Move the mouse pointer onto the image window. You can zoom into the image with your mouse. Use the sliders located at the right and bottom of the image window to select the image segment. Set the image display so that the start and end point of the calibration distance is displayed optimally on the monitor.

15.Set the calibration reference distance. The calibration reference distance is set differently for monocrystalline or polycrystalline standards:

•With a monocrystalline standard, a line is used to measure the calibration reference distance. Left click on the start and end points of the calibration reference distance.

•With a polycrystalline standard, the calibration reference distance is defined by the radius of a circle. The diffraction ring is measured by a 3-points circle. Insert the first two points by clicking with your left mouse button. Change the size of the circle by moving the mouse pointer. Click with the left mouse button to set the third point of the circle.

16.Click the right mouse button and select the Confirm Input command in the context menu.

•You will then return to the Calibrate Camera Lengths dialog box. In the diagram located at the top of the dialog box, the resolution [1/(nm*pixel)] is plotted against the camera length [mm]. It contains the first point with the calibration data that was just defined.

•You can now repeat the calibration process for further camera lengths.

Calibrating further camera lengths

17.Click the Set Calibration Distance… button again.

18.Set the next camera length, in the Microscope Control tool window.

19.Refocus if necessary and define the calibration reference distance.

20.Calibrate at least one more camera length in this way, 1850 mm for example.

Checking calibration data

21.You can check the calibration data directly in the Calibrate Camera Lengths dialog box. Take a look at the curve in the diagram at the top.

22.Click the Invert X-Axis button to check the linearity.

23.With an inverted axis, the curve should be largely linear, almost a line, and it should go through the origin.

•If the curve contains outliers that aren't on the line, you have to repeat the calibration for the corresponding camera length.

•As soon as the calibration data for at least three camera lengths is available, the Close button is replaced by the OK button.

24.Click the OK button to complete the calibration process.

25.You will then return to the Calibration dialog box. The status of the Camera Length calibration process is now Calibrated.

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