Table 1.

Measured grating periods for different positions of the object.

Acutal grating period, (m)	Measured grating period from experiment, ()
	mm	mm	mm	4f imaging
18.2	18.2 ± 0.21	18.3 ± 0.42	18.1 ± 0.65	18.5 ± 1.37
18.5	18.5 ± 0.20	18.4 ± 0.42	18.4 ± 0.64	18.7 ± 1.35
18.8	18.8 ± 0.20	18.6 ± 0.41	18.9 ± 0.62	19.0 ± 1.33
19.1	19.0 ± 0.20	19.3 ± 0.40	19.1 ± 0.61	19.3 ± 1.31
19.4	19.5 ± 0.19	19.3 ± 0.40	19.4 ± 0.60	19.6 ± 1.29
19.7	19.8 ± 0.19	19.7 ± 0.39	19.7 ± 0.59	19.9 ± 1.27