There are three effects of the lens curvature: - the location of the maximum AC signal is shifted which requires the adjustment of the z-axis IU position, in case the shift exceeds 1 mm - the image size on the detector changes resulting in the calibration change because of a fixed size of the photodetector aperture - the probe beam shifts across the detector while the lens is scanned. This problem could be solved either by point-by-point data acquisition, with the probe realignment at every new position of the sample, or by limiting the motorized scan distance.
The first effect happens because the lens shifts images positions along the probe path. The technology relies on the correct location of the object plane which should be translated to the photodetector plane by the Imaging Unit (IU). This shift could be approximated by the simple lens formula
