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MEMS-based displays enable always-on experience in wearables By Brian Gally Imagine if, when the first smartphones were being designed, there was no limiting factor around battery life. Think how differently each design decision could have been made. Would form factor be so standardized? Would the display need to turn off every few seconds after being idle? What kind of content and usage patterns would have developed around hardware that offered a completely open channel of content flow right into the pocket (or wrist, but we’ll get to that) of a consumer? Strangely enough, that movement toward a continuous flow of content has actually begun even with display-specific constraints ensconced. As connectivity through 3G, 4G and WiFi has become seemingly ubiquitous, so, too, has the computing prowess of our mobile devices. Sensors, chipsets, memory, display and power management are creating a highly contextual environment dictating how and which content is actually served. All the inertia described above, however, is actually still stymied by that modern mobile buzzkill – the black screen of a display turned off. Because, you see, this problem has not yet been solved. Devices are still constrained by their least efficient components: chief among them is the display. Modern displays (LCD or OLED and their variants) all must make certain tradeoffs. For the bright and colorful experience you want, you trade battery life and the ability to have that experience in brightly lit environments. While marginal improvements certainly continue to be hashed out in efficiency, the display still consumes upward (well upward in many cases) of 50% of the energy in a mobile device. Of particular interest is how this plays out in the new wideopen landscape of wearable computing. Looking at this category strictly from the perspective of the display technologies therein, there are seemingly two distinct camps. One says you can have your bright indoor device in exchange for charging daily (at least) and limited visibility outdoors. The other says you can have your outdoor-readable display and days of battery life, but at the expense of some mix of interactivity, color and pixel density. This is particularly interesting because the margin for error in a smartwatch is small for two reasons. First, a device worn on the body invokes a different consumer expectation. It should be thin and fashionable, of course, but from a technical perspective, it needs to be visible at a glance – indeed, always on – no matter where the user is. If the wearable screen is off, there is no appreciable difference than reaching into one’s pocket for their smartphone. And if the display is obscured by bright environmental light, like sunshine, always on is pointless. This is not a foreign concept to consumers. We all encounter various types of passive content every day. In fact, the very real estate the smartwatch seeks to fill was previously occupied by a passive content display – the wrist watch. No buttons to Fig. 1: The Qualcomm Toq smartwatch. push to activate the screen, just glance down and there is the information you need. The opportunity to leverage the great wave of contextually relevant data and serve it to the consumer in helpful and interesting ways is obviously the Holy Grail for the wearable and why most CE companies are clamoring to present their offering. Second, and more simply, the device is just much smaller. Smaller screens, smaller batteries. If product managers have been pulling their hair out for years managing the delicate balance of power allocation for a 2100mAh battery on a smartphone, a 210mAh battery is going to really give them fits. A wholesale change needs to happen. There is simply nowhere to hide a bigger battery on a wrist-worn device; the componentry must get more efficient. One solution, then, to unlocking the true potential of wearables and indeed the next generation of mobile experiences is a fundamentally different approach to the display component. A display that is reflective for great visibility even in the brightest of sunshine while being low power enough to enable days and days of usage while never going dark. This is, in a few words, the Qualcomm Mirasol display. The fundamental technology behind the Mirasol-branded display offerings from Qualcomm is called Interferometric Modulation (IMOD). IMOD technology offers an answer to what ails the nascent wearable space. Brian Gally is VP Product Management and Marketing at Qualcomm MEMS Technologies - www.qualcomm.com/mirasol Fig. 2: Qualcomm Mirasol display sub-pixel architecture, current generation. www.electronics-eetimes.com Electronic Engineering Times Europe February 2014 27


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