Fig. 4.
Cross correlation of focusing images at the tilted position. (A and B) Images acquired at a stage tilt angle of 60°. The beam was tilted along the tilt axis by 3 mrad. (C) Phase weighted cross correlation of the two images; the peak is highlighted with a circle. The images were acquired with a 0.05 s exposure at 29,000× magnification, and 4× binned to 1024 × 1024 pixels.