AQ-00073-000, Rev. 7 20
An example of the use of these tables is shown in Appendix C. In these measurements, Lab-
sphere SCS Spectralon color standards were measured using a dual beam spectrometer with a
single beam sphere accessory and a double beam spectrometer with a double beam sphere acces-
sory. The samples were chosen based on their wide reflectance variation across the wavelength
spectrum. In each case, the bottom curve represents the measured spectrum generated on the sin-
gle beam sphere. The ‘boxed’ curve represents the corrected values using the lookup tables. The
light curve is the actual reflectance of the standard as measured on the Lambda 19. The corrected
values, using the Substitution Error Correction Tables, give an excellent correlation with actual
double beam measurements.
Zeroline Correction
An integrating sphere is sensitive to small-angle scatter from the sample beam coupling optics.
The scattered radiation strikes the wall of the integrating sphere near the sample reflectance port,
creating a "halo" surrounding the port. This "halo-effect" gives rise to a small error in measure-
ment of reflectance factor which is most significant when measuring samples of very low reflec-
tance. Fortunately, this error is relatively easy to characterize and correct. The following
procedure may be used to correct reflectance factor measurements of diffuse or specular sam-
ples, in either the 8°/Hemispherical or 0°/Diffuse geometries:
300
0.512
0.571
0.636
0.691
0.730
0.773
0.791
0.825
0.895
0.912
0.956
0.964
325
0.505
0.571
0.631
0.691
0.725
0.774
0.792
0.827
0.898
0.915
0.965
0.971
350
0.500
0.569
0.627
0.692
0.722
0.775
0.790
0.829
0.899
0.917
0.970
0.975
375
0.495
0.568
0.624
0.691
0.718
0.771
0.789
0.827
0.898
0.917
0.974
0.978
400
0.492
0.568
0.623
0.692
0.716
0.774
0.789
0.832
0.899
0.918
0.978
0.983
425
0.491
0.567
0.622
0.693
0.715
0.775
0.790
0.833
0.899
0.918
0.980
0.985
450
0.490
0.568
0.623
0.693
0.714
0.774
0.791
0.833
0.900
0.920
0.981
0.986
475
0.491
0.568
0.624
0.695
0.715
0.775
0.793
0.835
0.902
0.921
0.983
0.987
500
0.491
0.569
0.624
0.696
0.715
0.776
0.794
0.836
0.902
0.921
0.983
0.987
525
0.492
0.570
0.626
0.696
0.716
0.775
0.795
0.837
0.903
0.922
0.983
0.988
550
0.493
0.570
0.627
0.698
0.716
0.777
0.797
0.839
0.904
0.921
0.983
0.988
575
0.495
0.570
0.628
0.698
0.717
0.776
0.798
0.840
0.905
0.924
0.983
0.987
600
0.496
0.571
0.629
0.698
0.718
0.776
0.800
0.840
0.906
0.923
0.983
0.988
625
0.497
0.572
0.631
0.699
0.719
0.777
0.802
0.841
0.907
0.924
0.983
0.987
650
0.498
0.572
0.632
0.699
0.719
0.776
0.803
0.841
0.907
0.926
0.983
0.988
675
0.499
0.572
0.633
0.701
0.720
0.777
0.805
0.843
0.908
0.924
0.983
0.988
700
0.500
0.574
0.634
0.702
0.721
0.778
0.806
0.843
0.909
0.925
0.983
0.988
725
0.501
0.575
0.635
0.702
0.721
0.776
0.807
0.844
0.910
0.926
0.983
0.988
750
0.503
0.576
0.637
0.703
0.722
0.778
0.809
0.845
0.911
0.926
0.983
0.988
775
0.504
0.575
0.638
0.704
0.723
0.778
0.810
0.846
0.912
0.926
0.984
0.987
800
0.506
0.576
0.640
0.704
0.724
0.777
0.812
0.846
0.913
0.931
0.984
0.990
825
0.507
0.578
0.641
0.704
0.725
0.777
0.813
0.848
0.913
0.930
0.983
0.988
850
0.508
0.578
0.642
0.704
0.725
0.777
0.813
0.848
0.913
0.930
0.982
0.990
875
0.509
0.578
0.644
0.705
0.726
0.778
0.814
0.848
0.912
0.929
0.981
0.988
900
0.511
0.578
0.645
0.706
0.726
0.779
0.814
0.851
0.912
0.930
0.980
0.988
925
0.512
0.579
0.646
0.707
0.727
0.781
0.815
0.851
0.913
0.930
0.980
0.987
950
0.513
0.579
0.647
0.709
0.728
0.781
0.817
0.851
0.914
0.930
0.980
0.988
975
0.515
0.579
0.648
0.710
0.728
0.781
0.818
0.851
0.914
0.931
0.981
0.989
1000
0.516
0.579
0.650
0.710
0.730
0.782
0.820
0.854
0.916
0.931
0.981
0.988
1025
0.517
0.580
0.651
0.711
0.730
0.781
0.821
0.854
0.917
0.932
0.982
0.986
1050
0.517
0.580
0.652
0.712
0.729
0.781
0.818
0.855
0.912
0.932
0.976
0.988
1075
0.518
0.582
0.652
0.713
0.728
0.783
0.816
0.854
0.909
0.931
0.971
0.986
1100
0.519
0.581
0.654
0.714
0.729
0.783
0.817
0.856
0.910
0.932
0.972
0.988
Wavelength Gray14/L2 Gray14/L19 Gray16/L2 Gray16/L19 Gray18/L2 Gray18/L19 Gray20/L2 Gray20/L19 Gray22/L2 Gray22/L19 Gray23/L2 Gray23/L19
Table 5. Reflectance values for gray Spectralon over 50%R.
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