Rugged-notebook vendor unveils 'sunproof' display

A new display technology from a maker of rugged computers promises finally to make touch screens readable in bright, direct sunlight.

Just as importantly, the new DynaVue display, from General Dynamics Itronix, creates a readable screen without draining more power from a notebook’s battery, and stays affordable.

The basic problem is that a display screen reflects exterior light, making the image appear faint and grey. Touch screens worsen the problem, because they consist of layers of glass and films, with each layer reflecting a percentage of light back to the viewer’s eyes. Itronix executives say that each layer reflects about 4% of the light, or 20% for the five layers of the screen assembly.

One solution is to boost the power of the underlying LCD’s, to brighten the screen. Asutek Computer adopted this approach earlier this year, using a different kind of light emitter. But this increased brightness creates only a slight improvement for outdoor touch screens. And some attempts to increase brightness suck a much larger amount of power from the notebook’s battery, says Tim Hill, Itronix senior marketing manager.

Instead, Itronix engineers focused on boosting the contrast ratio – the difference between the blackest blacks and the whitest white. The greater this difference, the more easily the human eye can see details, such as fine lines, says Ben Thacker, Itronix vice president of strategic marketing.

Specifically, Itronix focused on improving what’s called the contrast ratio for high-ambient light; in other words, for outdoor sunlight. A similar approach is taken by makers of so-called heads-up displays in jet cockpits, and of teleprompters. A high-definition TV for example can have a contrast ratio of 1000:1, but it’s designed for indoor, or low-ambient, lighting. “If you put an HDTV outdoors, you’re [left with a contrast ratio of] below 2-to-1,” Thacker says.

Itronix engineers, drawing on the cockpit-display expertise of General Dynamics’ Gulfstream jet aircraft unit, used polarizing technologies and “index-matching” films between the layers of the touch screen. Index matching is a way of reducing ambient-light reflections and increasing brightness. The result, Thacker says, is a display that’s easily viewable outdoors and can even be viewed with sunglasses.

According to a GD-Itronix document, the DynaVue display is somewhat less bright, at 400 nit (a standard measure of brightness), than the regular touch screen, at 500 nit. But DynaVue’s direct-sunlight contrast ratio is nearly four times greater, 8.86-to-1 compared with 1.95-to-1 for the conventional display.

The results are dramatic. In a recent demonstration outside of Network World’s headquarters, two GD-Itronix rugged notebooks were opened side by side, with screens positioned under a cloudless sky to receive the full glare of the sun. The standard screen dissolved into a bright gray murk: Colors were washed out (low-color saturation), and fine details were almost impossible to see. The DynaVue screen, though it appeared darker than it had indoors, still showed readable details and identifiable colors.