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Touchscreen touts texture perception

17 Jul 2014  | Julien Happich

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Smart devices may soon feature touchscreens with texture, paving the way for Braille reading for the visually impaired.

Researchers from Japanese touchscreen maker NLT Technologies disclosed how they were able to use a variant of electrovibration on a 4.1in wide touchscreen prototype to create localized friction (at multiple touch-points) and thus cause the perception of texture.

Based on what the researchers call a beat phenomenon of voltage waveforms, the company demonstrated regional electrostatic stimulation by using a matrix of transparent Indium Tin Oxide (ITO) electrodes over the display's glass substrate, covered by an acrylic insulator layer.

By driving the X (horizontal) and Y (vertical) electrodes at varying frequencies around 1kHz, the researchers were able to modulate the resulting electrostatic forces at the cross points, so as to obtain a localized stimulus in the excited regions and create different textures.

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When sliding your fingers across the display, this surface haptic effect reproduces skin sensations as if you were tracing actual objects on the display. With electrode pitches of 1.73mm (X) and 1.75mm (Y), the current prototype is able to emulate a given texture within an area covering multiple electrodes, roughly 4mm2 x 4mm2 to be felt correctly via skin sensation.

This multi-touch haptic effect can be synchronised with the actual image on the display, so that users can feel the appropriate texture as they would expect from touching the real object.

In a statement, the company claimed that the technology could easily scale up for larger higher touch-density displays for applications ranging from texture sharing across the web to cockpit displays in autos and aircraft, and for devices aimed at the visually impaired, though Braille reading would require a finer resolution (around 1mm2 discrete patches).

While power consumption is under investigation, response time seems inherently faster than alternative haptic solutions, we were told in an email exchange with the company. The main feature here is the regional stimulation, something that piezo-based haptics would not be able to provide at such a fine resolution.

 Electrostatic tactile display using beat phenomenon

Electrostatic tactile display using beat phenomenon of voltage waveforms between electrodes.

Now, creating the appropriate textures for such a haptic 2D display will require some form of automated image feature extraction, very much like for 2D to 3D content conversion, but adding tactile data on top of the display.

Last May, NLT Technologies also announced a new auto-stereoscopic display system relying on 3D eye-tracking to optimise parallax for an arbitrary viewpoint, so the company certainly has the knowhow to convert 2D content into a 2D + texture feel or 3D + tactile content.

When asked who would develop this, we were only told by the spokesperson: "I'm afraid that is confidential", which hints at further exciting announcements.

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