Minimum length scales of Metagrating3D

[mawc2019]

The minimum length scales of Metagrating3D estimated by ruler.py are 24.609375, 12.3046875, and 36.9140625, corresponding to the three design patterns in device1.csv, device2.csv, and device3.csv, respectively.

[mawc2019]

If the version based on the cv2 module is used, the estimated minimum length scales become 22.55859375, 14.35546875, and 49.21875, respectively.

[mawc2019]

Based on @mfschubert's version with ignore_interfaces = True, the estimated minimum length scales are 9 pixels, which amount to 26.19 or 26.25 nm.
With ignore_interfaces = False, the estimated minimum length scales are 3 pixels, which amount to 8.73 or 8.75 nm. The declared minimum length scale is 12 nm. For the first and the third design patterns, compared with previous estimations, the estimation here is much closer to the declared minimum length scale. However, because of ignore_interfaces = False, this estimated minimum length scale is probably associated with some interfacial features between solid and void regions.

[mawc2019]

All the above results are based on interpolated design patterns, which are not raw design patterns obtained directly from optimization. The minimum length scales of the raw design patterns estimated by ruler.py are 73.8 nm. If the version based on cv2 is used instead, the estimated minimum length scales are 65.6, 73.8, and 65.6 nm. If @mfschubert's version with ignore_interfaces = True is used, the estimated minimum length scales are 58.1 to 58.3 nm.