User`s guide

Gain Normalization

minutes for US1000 (2k x 2k) and US4000 (4k x 4k) respectively. Once the

procedure completes, a reference image is stored in DigitalMicrograph

“Reference Images” folder for later use.

Typically it is not required to run this routine frequently.

It is important to run Gain normalization routine (next section) after Prepare

Quadrant Correction Reference in order to activate the linearization

correction routine, so that it is applied to all the future acquired images.

2.5 Gain Normalization

It is important to prepare a new gain reference image after the CCD has reached

the equilibrium temperature (normally this takes about 1-2 hours). The gain

reference image should be checked regularly.

To prepare gain reference image, remove specimen from the field of view,

evenly spread the illumination across the CCD sensor.

Under the Camera menu (Figure 2-3), choose Prepare Gain Reference. Set

the target intensity to the value of 10,000-20,000 (for US4000, it may be

necessary to set the target intensity close to 10,000 counts since the CCD may

saturate around 20,000 counts. See the “Most Often Asked Questions” in

section 5 for details). Normally it is sufficient to set the frames to average to 4.

Then simply follow the instructions on the screen.

It is recommended to perform this operation when

• The camera temperature is stable (check the temperature display on the

controller front panel),

• Every time the camera is switched on,

• Once a week if the camera is always on, or

• Before acquiring any important images.

2.6 Magnification Calibration

The displayed nominal magnification on TEM is for photographic film and has

an accuracy of 5-10%. The CCD camera is located on a different plane (height

wise) respect to the film camera. As a consequence, the magnification must be

calibrated. The calibration is done using Reference calibration samples.

At “Low” magnifications:

• Use “cross grating sample” or any sample having known spacing

At “High” magnifications:

UltraScan User’s Guide Reference Series Rev 1.0 2-7