Bradley M. Ratliff and Garrett C. Sargent, "Alternative linear microgrid polarimeters: design, analysis, and demosaicing considerations," Appl. Opt. 60, 5805-5818 (2021)
Linear division of focal plane (DoFP), or integrated microgrid polarimeters, provide a measurement strategy for obtaining time-synchronized polarized intensity measurements across a scene. This is accomplished by masking pixels in the focal plane array sensor with a repeating pattern of different linear polarizers. The convention in industry has been to use a repeating $2 \times 2$ pattern of four linear polarizers with chosen polarizer orientation angles of ${\{0,45,90,135\} ^ \circ}$. Alternative designs based upon other $P \times Q$ modulation patterns have been proposed that demonstrate improved performance over conventional microgrid arrays due to better utilization of bandwidth in the frequency domain. Here, we develop a model for linear DoFP snapshot polarimeters that provides an in-depth understanding of these devices in both the spatial and frequency domains and relate this model to previously reported generalized DoFP channeled polarimeter models. We then use the model to identify practical modulation patterns and study their performance through empirical simulations based upon data collected from real polarimeters. We demonstrate the validity of the developed model and compare the performance of the identified modulation schemes against a common set of ground truth images. We find that choosing alternative sets of polarizer angles, in conjunction with modulators that improve bandwidth usage, result in the best overall designs that can improve performance over conventional microgrid polarimeters.
Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.
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Coefficient Matrices for the , , and Modulation Schemesa
The right column indicates the spectra locations corresponding to each row of ${\textbf{C}}$.
Table 2.
Polarizer Angle Permutations for the and Cases that Yield and Spectra at the Locations Indicated in Fig. 3a
Permutations
Permutations
The sign and real or complex component is indicated above each permutation. The permutations indicated by $^\dagger$ were reported in [35] and $^{\dagger \dagger}$ in [34].
Table 3.
Intensity Measurements that Result from Each Indicated Polarizer Angular Set
Table 4.
Mean PSNR and GMSD Scores Relative to Ground Truth for Stokes Images Estimated with Eq. (19) Using DoT Intensity Images from the Indicated Angular Set
PSNR
SSIM
GMSD
Image
64.731
66.558
68.148
0.9998
0.9999
0.9999
0.0005
0.0005
0.0001
51.734
54.827
55.896
0.9933
0.9937
0.9966
0.0048
0.0030
0.0023
53.121
54.905
57.347
0.9929
0.9933
0.9962
0.0037
0.0027
0.0021
DoLP
37.292
38.256
40.217
0.9053
0.9142
0.9455
0.0194
0.0168
0.0122
AoP
14.141
14.743
15.726
0.5324
0.5597
0.6496
0.1974
0.1835
0.1611
Table 5.
Mean PSNR and GMSD Scores Relative to Ground Truth for Stokes Images Estimated from Microgrid Intensity Images Simulated According to Eq. (3)
PSNR
SSIM
GMSD
Image
50.054
50.070
50.075
50.071
0.9952
0.9953
0.9953
0.9953
0.0020
0.0019
0.0018
0.0019
49.117
51.835
51.160
50.703
0.9864
0.9936
0.9924
0.9911
0.0191
0.0072
0.0094
0.0114
49.095
49.120
51.774
51.385
0.9848
0.9847
0.9916
0.9903
0.0206
0.0204
0.0098
0.0114
DoLP
36.672
37.148
38.443
38.176
0.9153
0.9242
0.9359
0.9331
0.0490
0.0445
0.0340
0.0362
AoP
14.715
14.929
15.674
15.573
0.5153
0.5410
0.5679
0.5606
0.2037
0.1947
0.1747
0.1779
Table 6.
Mean PSNR and GMSD Scores Relative to Ground Truth for Stokes Images Estimated from Microgrid Intensity Images Simulated According to Eq. (21)
PSNR
SSIM
GMSD
Image
49.910
49.990
49.991
49.926
0.9952
0.9952
0.9952
0.9952
0.0022
0.0022
0.0023
0.0021
47.233
50.430
49.785
48.180
0.9843
0.9918
0.9908
0.9890
0.0209
0.0091
0.0108
0.0138
47.836
48.009
50.657
49.583
0.9829
0.9831
0.9899
0.9883
0.0220
0.0231
0.0111
0.0132
DoLP
34.723
35.476
36.485
35.662
0.8816
0.8988
0.9098
0.8982
0.0615
0.0565
0.0478
0.0512
AoP
13.412
14.030
14.518
13.874
0.4475
0.4884
0.5084
0.4814
0.2407
0.2190
0.2076
0.2252
Tables (6)
Table 1.
Coefficient Matrices for the , , and Modulation Schemesa
The right column indicates the spectra locations corresponding to each row of ${\textbf{C}}$.
Table 2.
Polarizer Angle Permutations for the and Cases that Yield and Spectra at the Locations Indicated in Fig. 3a
Permutations
Permutations
The sign and real or complex component is indicated above each permutation. The permutations indicated by $^\dagger$ were reported in [35] and $^{\dagger \dagger}$ in [34].
Table 3.
Intensity Measurements that Result from Each Indicated Polarizer Angular Set
Table 4.
Mean PSNR and GMSD Scores Relative to Ground Truth for Stokes Images Estimated with Eq. (19) Using DoT Intensity Images from the Indicated Angular Set
PSNR
SSIM
GMSD
Image
64.731
66.558
68.148
0.9998
0.9999
0.9999
0.0005
0.0005
0.0001
51.734
54.827
55.896
0.9933
0.9937
0.9966
0.0048
0.0030
0.0023
53.121
54.905
57.347
0.9929
0.9933
0.9962
0.0037
0.0027
0.0021
DoLP
37.292
38.256
40.217
0.9053
0.9142
0.9455
0.0194
0.0168
0.0122
AoP
14.141
14.743
15.726
0.5324
0.5597
0.6496
0.1974
0.1835
0.1611
Table 5.
Mean PSNR and GMSD Scores Relative to Ground Truth for Stokes Images Estimated from Microgrid Intensity Images Simulated According to Eq. (3)
PSNR
SSIM
GMSD
Image
50.054
50.070
50.075
50.071
0.9952
0.9953
0.9953
0.9953
0.0020
0.0019
0.0018
0.0019
49.117
51.835
51.160
50.703
0.9864
0.9936
0.9924
0.9911
0.0191
0.0072
0.0094
0.0114
49.095
49.120
51.774
51.385
0.9848
0.9847
0.9916
0.9903
0.0206
0.0204
0.0098
0.0114
DoLP
36.672
37.148
38.443
38.176
0.9153
0.9242
0.9359
0.9331
0.0490
0.0445
0.0340
0.0362
AoP
14.715
14.929
15.674
15.573
0.5153
0.5410
0.5679
0.5606
0.2037
0.1947
0.1747
0.1779
Table 6.
Mean PSNR and GMSD Scores Relative to Ground Truth for Stokes Images Estimated from Microgrid Intensity Images Simulated According to Eq. (21)