The amplitude of a resonant scanner does not always change linearly with the control voltage. Since the galvanometric mirror for the scan in y-direction has a linear response, this can lead to an image distorton in x-direction at different zoom levels.
ScanImage has a built in tool to correct for the non-linear amplitude of the resonant scanner. To access this feature, execute the following command in the Matlab command prompt:
This will show the Resonant FOV to Voltage Calibration Curve, which allows you to manipulate the zoom-to-voltage lookup table for the resonant mirror. After enabling the feature with the checkbox in the lower left corner, start a focus and adjust the zoom level until the distortion becomes visible. In the calibration window, add a control point and adjust the control point's position using the arrow buttons until the distortion is removed. Repeat the process for multiple zoom levels.