Edited by Shunsuke Kobayashi, Shigeo Mikoshiba, and Sungkyoo Lim
© 2009 John Wiley & Sons, Ltd.
Reviewed by Munisamy Anandan
Liquid-crystal-display (LCD) backlighting is a rapidly advancing field. Progress in every component of backlight systems – light sources, drive electronics, light guides, optical films, and assemblies to house all these components – is being made at galloping speed. It can be difficult to keep pace with all the developments and equally difficult to find information from a single source: the literature appears in various journals and conference proceedings. In this context, LCD Backlights is an invaluable resource for researchers and general readers alike.
The book has a few shortcomings. Even while it was being written, LCD-backlighting technology was rapidly advancing. Therefore, although most of the information is reasonably well updated, some is not. In certain chapters, acronyms such as OLED, CCFL, and PDP are not defined, which would have been especially helpful to general readers. And a few chapters lack sufficient references, while one has none at all.
LCD Backlights is organized into two parts and 21 chapters. Each chapter is authored by different experts in the field. Part 1, Backlight by Use, examines different ways that backlighting is being employed in areas such as LCD TVs, notebook PCs, and handheld data terminals. Part 2, Light Source Devices, looks at CCFLs (cold-cathode fluorescent lamps), HCFLs (hot-cathode fluorescent lamps), EEFLs (external-electrode fluorescent lamps), and many other types of light sources.
The first chapter, "Technical Trends and Requirements/Specifications for LCD-TV Backlights" provides a good general overview of LCD backlighting. Different light sources are reviewed according to merit, and the structure of backlighting with various components is clearly illustrated. The author makes a clear comparison between the technology of CCFLsand LEDs with regard to their generation of color gamut and correctly emphasizes the potential of LEDs as compared to other light sources.
One chapter in Part 1 that contains information that is seldom found is "Multiple Primary Color Backlights," which discusses widening the color gamut through multi-primary colors of LED light sources and employing LEDs with correct sequences of driving. The author also describes the change in the peak wavelength of LEDs with ambient temperature, which is very relevant to this topic.
A discussion on motion blur in another chapter describes techniques of black-frame insertion and backlight blinking/scrolling/dimming combined with increases in frame rate, but does not mention the recent trend in increasing the frame rate to 240 Hz.
"Reduction of Backlight Power Consumption of LCD TVs" is authored by the co-inventor (with the editor of this book) of the Adaptive Dimming Technique (ADT), and therefore emphasizes ADT. The two writers have also published a paper on 0D, 1D, and 2D dimming. Lately, this technique has come to be known as "local dimming," which is commercially very popular in modern LCD TVs. The concept of ADT is well illustrated here with photographs.
Part 1 finishes up with practical information about the fabrication of a light guide for notebook PC/monitor backlights and LED backlights for handheld data terminals.
Part 2 looks at a variety of light sources for backlights, such as CCFL (featuring some seldom-reported information on the surface temperature of long CCFLs in a single-end mode of driving), and HCFL.
The sections on EEFL, FFL (flat-fluorescent lamp), and mercury-free fluorescent lamps contain some information that has not been updated. EEFLs are no longer used in LCD backlights, for example. However, the author makes interesting comparisons between CCFLs and EEFLs. The authors of the chapter on FFL do not refer to the fact that FFLs are not used in commercial backlighting for LCD TVs. The technique adopted for fabricating the channels of the "serpentine" lamp is well described, however. As for mercury-free fluorescent lamps, they are also not used in today's commercial backlights for LCD TVs.
A chapter on the historical development of the "electrode-less lamp" is interesting to read, despite the fact that this type of lamp is also not commercially used for LCD backlights. Readers may find the content more appropriate for a book on fluorescent lamps than on backlighting.
"LED Backlights" and "Technological Trends of LED Backlight Units" describe more current backlight solutions, and a chapter on white-OLED (organic light-emitting-diode) backlights provides information about R&D efforts at various academic institutions and industries throughout the world. This chapter should be of particular interest to the research community. White-light emission from light-generating host layers of single- and double-layered configurations is well illustrated, and the state of the art on white OLEDs, in general, is well brought-out. What is missing is a simple white-OLED backlight structure, as well as a description of its performance to demonstrate the advantage of a white-OLED backlight over an LED backlight in terms of the simplified flat light source of a white OLED that does not require optical light guides and films. White OLEDs are not commercially employed for backlighting LCDs, but this approach has a bright future.
The book ends with chapters on inorganic EL (electroluminescent) backlights, field-emission backlights, light-guide plates, optical diffuser plates, lens films, and reflective-polarization films.
LCD Backlights includes an impressive spectrum of topics. Having specialized for nearly 10 years in this field, I can attest to the fact that it would be hard to find anywhere else the range of backlighting technology and information covered in this book.