tailieunhanh - Features of Liquid Crystal Display Materials and Processes Part 11

Tham khảo tài liệu 'features of liquid crystal display materials and processes part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Portable LCD Image Quality Effects of Surround Luminance 189 MTF u sin nu nu sin c nnu 8 where 3 - denotes the Fourier transform of the argument. Viewing flare can be defined as the additional luminance due to surface reflections off the front of a display caused by ambient illumination. It boosts the PSF by a constant offset level as illustrated in Fig. 5 b thus the zero frequency response or dc component is increased only and other frequency responses remain the same if the signal is transformed into Fourier domain. When the MTF is normalised at the maximum MTF 0 1 and MTF u 0 is multiplied by a weighting factor a for u 0 as shown in eq. 9 . MTF u aMTF0 u a sin c nnu 9 where i represents the amount of viewing flare. For instance of this MTF0 shows the MTF for dark viewing condition so MTFi is the MTF for a viewing condition where the amount of viewing flare is i cd m2. The weighting factor a refers to the ratio of zero frequency response between MTF0 u and MTFi u as given in Eq. 10 . Practically mean value of the PSF can be simply used instead of calculating zero frequency response of the MTF in Fourier domain therefore a values should be identical to the relative Michelson contrast to the dark viewing condition as can be expected See Table 1 . MTFo 0 LMax 0 LMin 0 2 MTFi 0 LMaxi LMini 2 10 The estimated MTF of the LCD monitor used in this study is presented in Fig. 6 See the solid line . Single-pixel size of the LCD is set to be in visual angle unit. The estimated MTFs for the higher illumination levels are shown in Fig. 6 as well represented by dashed and dotted lines. Spatial Frequency cycles per degree Fig. 6. MTF of the LCD used in this study and the approximated MTFs under two different levels of viewing flare. Single-pixel size of the LCD is set to be in visual angle unit. The compensation factors a for viewing flare for the three viewing conditions are listed in Table 3. 190 Features of Liquid Crystal Display Materials and Processes Dark .