The name is absent

38

measurements (n)

Figure 4.5 : The estimated thickness of the plastic plate, versus number of measure-
ments (n) used in CS reconstruction for the object in Figure 4.4. Dashed line indicates
the actual thickness difference (1.73 mm), as determined using a micrometer. The
thickness estimates rapidly converge to the correct answer with increasing n.

the amplitude image shows almost no contrast, the phase image shows a sharp con-
trast between the upper and lower halves of the rectangular aperture. The thickness
difference (∆d) can be estimated from the measured phase difference (Δ0) according
to ∆θ = ^ω^ⁿ~T^∙-_ι which is valid since the plastic is essentially dispersionless. The ac-
quired data follows a linear relationship of ∆θ versus frequency, and the slope of that
line is used to estimate ∆d. Figure 4.5 shows the estimated value, for an increasing
number of CS measurements from 200 to 600. Compared to the value ∆d = 1.73 mm
determined with a micrometer, Figure 4.5 shows that the estimation results rapidly
converge to the correct answer, even for a small number of CS measurements. Another
reconstruction algorithm which assumes smoothness in the phase image yields even
better results [72]. Other recently developed algorithms for complex images might
even achieve better reconstruction results [73].

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