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Abstract— A dual‐cell‐gap transflective liquid‐crystal display (TR‐LCD) with identical response time in both the transmissive and reflective regions is demonstrated. In the transmissive region, strong anchoring energy is used to decrease the response time, while in the reflective region, weak anchoring energy is used to increase the response time. And overdrive voltage technology is adopted to make the response time identical in both the transmissive and reflective regions. The device structure and operating principle of the TR‐LCD was analyzed, the anchoring energy in the transmissive and reflective regions was designed, and the response time and electro‐optic characteristics of the TR‐LCD was calculated. The simulated dual‐cell‐gap TR‐LCD demonstrated good performances.

The peak wavelength of light-emitting-diodes (LEDs) shifts towards the longer wavelengths when the temperature of the LED chip increases. The color-rendering index (CRI) and luminous efficacy may change with the peak wavelength of the LED, and it is not expected to do so when the LEDs are used in fields which require a high CRI and luminous efficacy. A mathematical model of the LED spectrum was used to analyze the influence of the wavelength shift on the CRI and luminous efficacy of three-and four-chip-packaged LEDs, respectively. The results show that the CRI decreases with the peak wavelengths shifting towards longer wavelength for both three-and four-chip LEDs; especially, the CRI of the four-chip LEDs decreases more for a green-color wavelength shift than for other colors. The luminous efficacy increases with a green-color wavelength shift and decreases with a red-color wavelength shift. FIGURE 5 -The normalized CRI as a function of shifted wavelength for the four-chip LED.FIGURE 6 -The luminous efficacy as a function of shifted wavelength for the four-chip LED.FIGURE 4 -Spectral power distribution of the four-chip LED. Journal of the SID 18/12, 2010 1031 13 S. Chhajed et al., "Influence of junction temperature on chromaticity and color-rendering properties of trichromatic white-light sources based on light-emitting diodes," J. Appl. Phys. 97, 054506 (2005). 14 Y. Ohno, "Color rendering and luminous efficacy of white LED spectra," Proc. SPIE 5530, 88-98 (2004). papers on display devices and systems. She holds three U.S. patents and five Chinese patents. She is a senior SID member. Her recent research interests include optics and optoelectronics, especial display technologies. Jin-Ren Yan is a graduate student at the School of Electronics and Information Engineering, Sichuan University. His major is optical engineering. His recent research interest is information-display technologies. Lei Li is working toward his Ph.D. degree at the School of Electronic and Information Engineering, Sichuan University. He has published four papers. His major is optical engineering. His recent research interest is information-display technologies and optical design. Da-Hai Li is a professor of optics at the School of Electronics and Information Engineering, Sichuan University. He received his M.S. degree from the University of Electronic Science and Technology of China in 1996 and Ph.D. degree from Sichuan University in 2002, respectively. He has published more than 40 papers. He is a member of the Society for Information. His recent research interests include optics and optoelectronics, especially display technologies and optical measurements.Jian-De Zhang is a graduate student at the School of Electronics and Information Engineering, Sichuan University. His major is optical engineering. His recent research interest is informationdisplay technologies.

A reflector-based light-emitting diode (LED) luminaire structure that can achieve a large cut-off angle for general lighting is presented in this work. The proposed lighting unit mainly consists of a spherical reflector and a primary packaging lens that contains an aspheric surface and a spherical surface. The light rays emitted from the LED light source are well controlled by the spherical reflector and the aspheric surface of the lens for the purpose of obtaining a uniform illumination on the target surface. Both the ideal Lambertian LED and non-Lambertian LED light sources were employed to validate the proposed structure and the performance of the designed lighting units was analyzed by optical simulation. The results show that the light utilization efficiencies and the estimated uniformities are 92.96% and 91.11% for ideal Lambertian LED-based lighting unit and 93.31% and 91.64% for non-Lambertian LED-based lighting unit, respectively. Further analysis shows that the tolerances of horizontal, vertical, and rotational deviation of the both lighting units were about 2.0 mm, 1.0 mm, and 1.0°, respectively.

In this work, a scheme of combining an aspheric reflector and a primary packaging freeform lens in phosphor-converted lighting-emitting diode (pc-LED) based lighting system design was developed. In contrast to most of previous works in which the color and illumination uniformity of the pc-LED lighting systems were improved one by one, the developed scheme can improve both indicators simultaneously. To demonstrate the feasibility of the developed design scheme, an initially designed pc-LED optical model, with an average correlated color temperature (CCT) of about 5000 K, was constructed as the light source of the illumination system. The key ingredient to the color uniformity of the illumination system was investigated at first, and then several instances with the cut-off angle ranging from 40 to 60 degrees were further discussed. Detailed analysis shows: for each case, the CCT variation decreases from over 4000 K to smaller than 300 K and the illumination uniformity increases from a very low level to better than 80% on the target region.