Results
Table 1 shows a summary of the results. The first column lists the 15 CRT colors and 9 filter colors measured. The second column contains the colorimetric information measured by the reference spectroradiometer and luminance meter. The third column compares the readings of the tristimulus colorimeter to the reference spectroradiometer before applying any matrix corrections. The colorimeter readings are based on a calibration using the first CRT color (white). The chromaticity differences for some colors exceed 0.010, and the luminance differences range over several percent.
Three different R¢ matrices were computed. The first was computed following the procedure given in ASTM Standard E 1455-92. The first eight CRT color measurements were used as the input data. The second R¢ matrix was computed using the same eight CRT colors as the sample colors, but following the procedure introduced in this work, above. The third R¢ matrix was computed similarly using the first four CRT colors and the first four glass-filter colors (including that of the diffuser alone).
The next three columns in Table 1 show how the differences between the reference and target instruments narrow for the three R¢ matrices. In each column, one of the matrices is applied to measurements of all the CRT colors and the glass-filter colors. For the CRT measurements, the results are summarized in two ways: the differences including those samples that went into the computation of R¢, and those excluding those samples. For the filter-glass measurements, the summary includes all 9 samples. In each case, the RMS and maximum differences are shown.
The results show that all three R¢ matrices provide significant improvement in the operation of the tristimulus colorimeter. The measurements of the filtered-glasses also improved with the two R¢ matrices that were based solely on the CRT measurements. In these two cases, for the CRT measurements, the RMS differences in x, y were all £ 0.001. The new minimization technique (column 5) is seen to yield better results than the ASTM formula (column 4). Additional analysis shows that much of this improvement with the minimization in (x, y, Y) space arises due to common mode noise in the (X, Y, Z) values of a single measurement (e.g., from display flicker). The data in the last column show a good compromise between improvements in the CRT measurements and improvements in the measurements of the colored glasses. |
