# Reducing the Power Consumption of VR Displays with a Field Sequential Color LCD
## 3 Simulation Results
To characterize the FSC LCD, contrast ratio, color gamut, and color shift are sequentially simulated. Light engines play a significant role in determining the system contrast ratio. Because of the depolarization from TFT circuits, LCs, and color filters, the contrast ratio of the FFS mode is limited to ~2500:1. For this reason, the FSC LCD can exhibit a higher contrast ratio by eliminating color filters. We use a positive A-plate and negative A-plate as compensation films [28]. Figure 7 depicts the simulated isocontrast contour at \(\lambda\) = 550 nm. A high contrast ratio (~1000:1) region expands to ~20\({}^{\circ}\) viewing cone, which is usually adequate for VR applications. Color gamut and color uniformity are also critical to the performance of light engines. In the Meta Quest Pro, quantum dots (QDs) are used in the LCD's backlight module. Therefore, we compare the FSC LCD using RGB LEDs [29] with the LCD using a QD color conversion layer and pigment color filters [30] in terms of color gamut and color shift. Besides pigment color filters, the color can also be generated by the band gap shifting of a cholesteric liquid crystal [31]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & & & **Rise Time (ms)** & & \\ \hline \multirow{4}{*}{Decay time (ms)} & Gray level & 0 & 64 & 128 & 192 & 255 \\ \cline{2-6}  & 0 & \(\backslash\) & 2.17 & 1.97 & 1.77 & 1.74 \\ \cline{2-6}  & 64 & 0.62 & \(\backslash\) & 1.75 & 1.64 & 1.84 \\ \cline{2-6}  & 128 & 0.65 & 1.65 & \(\backslash\) & 1.60 & 2.07 \\ \cline{2-6}  & 192 & 0.69 & 1.58 & 1.61 & \(\backslash\) & 2.50 \\ \cline{2-6}  & 255 & 0.75 & 1.51 & 1.57 & 1.60 & \(\backslash\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulated response time of FFS mode between different gray levels without overdrive and undershoot. The operating temperature is 50 \({}^{\circ}\)C.  
Figure 6: Simulated voltage-dependent transmittance at \(w\) = 1.5 \(\upmu\)m, \(g\) = 1.5 \(\upmu\)m, and \(T\) = 50 \({}^{\circ}\)C.  
Figure 8a shows the spectra of RGB LEDs used in the FSC LCD; while Figure 8b depicts the spectra of a blue LED, green QDs, and red QDs employed in the backlight module of the LCD. The color gamut of FSC LCD is mainly limited by the broader emission spectrum of the green LED, as shown in Figure 8a. For an InGaN-based LED, its spectral bandwidth increases as the peak emission wavelength increases because of the increased indium concentration [32]. In contrast, the red-color III-phosphides LEDs exhibit a relatively narrow spectral bandwidth and high efficiency. For the LCD using color filters, the crosstalk caused by the overlap between the backlight's spectrum in Figure 8b and color filters hinders a wider color gamut [33]. Therefore, their color gamut is comparable: the FSC LCD can cover 96.2% DCI-P3 while the LCD using color filters can cover 96.4% DCI-P3. The color gamut of the FSC LCD can be further enlarged using a green LED with a narrower emission spectrum. Incomplete switching of the LC can cause shrinkage of the color gamut; thus, a larger color gamut also helps mitigate the demanding requirement of LC response time. For color shift, the horizontal (\(\phi\) = 0\({}^{\circ}\)) and vertical (\(\phi\) = 90\({}^{\circ}\)) viewing directions are usually reported experimentally. To calculate color shift, we first extracted wavelength- and angle-dependent transmittance from TechWiz and then multiplied it by the backlight's spectrum and the transmittance spectra of the color filters. Figure 9a,b shows the simulated color shift for FSC LCD and LCD with color filters, respectively. In both types of LCDs, blue colors in the vertical direction have the largest color shift (\(\Delta u^{\prime}v\)), followed by green  
Figure 8: The spectra of (**a**) RGB LEDs used in the FSC LCD, and (**b**) a blue LED, green QDs, and red QDs in the backlight module of the LCD. Figure 7: Simulated isocontrast contour for single-domain FFS mode using TechWiz software. The operating temperature is 50 \({}^{\circ}\)C.  
and red.