Leia aims to bring interactive holographic displays to your phone

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Now that the Dick Tracy wristwatch is nearing reality, is it time for holographic Star Wars-style messaging to make its debut? HP Labs spinout Leia believes it is. Using a clever system of diffraction gratings, its small displays produce 64 different versions of each image, allowing a viewer to move around an object or person shown on the display as if it was right in the room with them. CEO David Fattal spoke to an eager crowd of imaging researchers at Stanford University about his company’s progress since it separated from HP. While the concepts behind Leia are the same as when the team’s work at HP was first published in Nature last year, the new company now has full color prototypes with improved resolution as it prepares for a product launch.

Diffraction: Using 3D to “fake” a hologram

Key to Leia’s technology is the use of fairly simple diffraction gratings at each pixel to redirect the backlight in different directions. The gratings are created by etching grooves in a thin sheet of glass. Placed under a conventional LCD, the gratings create as many as 64 different points of view — in an eight-by-eight grid. Because it uses only diffraction, Leia’s system can calculate the needed light field in real time — much faster than more complex interference-based hologram generators. To complement the gratings, Leia has created a specialized, programmable LED backlight that it also manufactures.

Fattal claims that Leia’s diffraction-based system is much more efficient than traditional parallax barriers and lenticular designs for multiple position glasses-free 3D. He says it is also much easier on the CPU than the eye-tracking approach Amazon is rumored to be using for its planned smartphone. One other advantage Leia’s technology has over the eye-tracking approach is that Leia’s displays can be viewed by several people at once. Leia has also already coupled one of its prototypes with a Leap Motion sensor, allowing the creation of interactive applications.

Until now, the problem for diffraction-based solutions has been resolution. Since each pixel needs to be projected in 64 different ways, the display resolution is reduced by an equivalent amount. With LCD makers racing past 500 PPI in mobile displays, Leia is betting that some of that additional resolution can easily be sacrificed for the added value of an interactive 3D display. Leia also needs to address color. Early prototypes have all been monochrome, although Fattal says the company has been prototyping both time-sliced color displays — using very high refresh rates to alternate between colors — and spatially-divided displays, which would of course complicate matters by further reducing resolution in exchange for adding color.

Making HoloChat A Reality

Since the output of its display is 64 different points of view, Leia has been able to build a matching input device using an array of 64 mobile cameras in a simple 3D printed frame. The combination may become the world’s first mobile Holochat device. Each camera maps directly to one of the 64 sets of pixels in the display, so very little image processing is needed in between. That allows Leia to create realtime interactive 3D displays, like the one Fattal is explaining in the accompanying photo — where a moving hand is mapped instantly into 64 different views that can be sent to one of its displays.

In addition to use in mobile computing, Fattal sees applications for Leia’s technology inmedicine, home automation, and car infotainment systems. The company is already actively courting developers, with a programming toolkit that allows simple conversion of WebGL objects into Leia-displayable ones with only a small amount of additional code. The company is still working closely with HP, and in fact has its factory co-located there, but it is ramping up its production operation in Suzhou, China. If Fattal is right that mobile display manufacturers have resolution to burn in their upcoming product cycles — and Leia can solve the problem of driving its display in full color at standard video frame rates — then look to see Holochat coming to mobile devices in the near future.

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