Monochrome LCDs offer power, cost advantages over color TFT counterparts

May 18, 2017 // By Paul Hooper
Thinking creatively about the needs of the user interface can help meet challenging power and cost targets when designing products for use in environments ranging from homes or offices to cars or factories.

Power consumption and bill of materials are important factors in many design projects. If either is too high there may be pressure to compromise on some features. The user interface could become a target: a colour TFT-LCD can be resource-hungry, but the look and feel are critical if the product is to be popular and successful.

Not all end-product applications need a TFT-LCD. The latest monochrome display technologies can provide good alternatives when applied thoughtfully, and can lower the demands on system resources while still ensuring a great user experience.

Close the gap with advanced technologies
Monochrome LCD displays have improved in many ways since the end of the 2G-mobile era. Designers can choose from a wide variety of display types, and newer technologies such as Fast-Response (FRSTN) and film-compensated FSTN or FFSTN types, deliver faster response times, sharper images, higher contrast and wider viewing angles than older, standard STN displays. Dual-Scan DSTN displays have also been introduced, which achieve higher image quality by effectively doubling the line-refresh rate.

Fig. 1: Vertical alignment display with true
black background and a high contrast ratio.

Vertical alignment displays with true black background are another exciting new development in monochrome LCDs. These can achieve a contrast ratio of more than 1000:1, and deliver sharp image quality as well as wide viewing angles. Almost any backlight colour can be used to deliver the required visual effect.

Crisp white backlighting, for example, can be impressive and easy to read, and selective colour is also possible through special backlight design or with optical filters. Inventive use of selective colour can provide an efficient and cost-effective way of making a warning graphic stand out against simple and straightforward characters or graphics.

Figure 1 shows how this type of display can be engineered to deliver a powerful visual impact.

Although TFT-LCD still has the edge in terms of image quality, and faster response improves handling of moving graphics such as a mouse pointer, the performance gap between monochrome and TFT-LCDs has narrowed.

By concentrating on meeting the needs of the application, such as the use of colours, likely viewing angles, or any need for fast-moving images or icons, a monochrome display can be engineered to deliver a high-quality user experience in applications ranging from consumer products to professional electronic equipment and automotive displays.

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