experimental data

(a) and(b) are interferograms acquired near the short focus with shear ratios of s1 = 0.67, where (a)is the interferogram acquired without the test element and (b) is the interferogram acquired with the test element, and (c) and (d) are interferograms acquired near the long focus with shear ratios of s2 = 0.77, where (c) is the interferogram acquired without the test element and (d) is the interferogram acquired with the test element. interferograms acquired with the test element.