017-018-019_EETE-VF

EETE DECEMBER 2012

DESIGN & PRODUCTS DISPLAYS & INTERFACES The modern automotive display touch-lens interface By Paul Weindorf, James Kornacki The cenTer sTacK panel area of today’s vehicles has be- come the integration site for many occupant interface technolo- gies and is being driven by consumer requirements influenced by today’s personal electronic devices. The display interface is an area of particular focus in the automotive industry as poke- through resistive touch displays yield a more modern touch-lens in the integrated center control panel – see figure 1. Display interface requirement considerations for the touch- lens include functional, aesthetics, and performance & confor- mance categories. Figure 2 shows a representation of these interface requirements (green), enablers (yellow), and the key component (pink) of the system. addressing all of these con- siderations within the touch-lens component for automotive use significantly shrinks the solution space due to competing requirements that can be grouped in the following categories: •Functional – multi-touch sensing, touch with press-for-intent, force feedback haptics, and spatial gesture recognition •Aesthetics – dead-front look, minimize fingerprints, seamless front surface, and curved surface Fig. 1: Touch-lens in integrated center control panel. •Performance & Conformance – display visibility, acceptable birefringence, head impact regulatory compliance, and environmental performance. Functional requirements a high craftsmanship feel is generally provided by a hard surface. Therefore a curved touch-lens over an 8-inch display requires a birefringence-free polymer lens base material thick- ness of at least 2 to 2.5mm that impacts the selection of the touch technology. Projected capacitance (pro-cap) screens can be adapted to provide a high craftsmanship continuous curved surface touch- lens desired by automotive styling studios. Integrating the touch screen into a curved surface eliminates resistive touch screen, most infrared LeD, and acoustic wave technologies as solutions since these technologies require a flat surface to operate. Tech- nology companies are working on infrared and acoustic wave technologies for continuous curved surface touch solutions that may become suitable for automotive applications in the future. Audible and tactile feedback augments the verification that the touch has been registered. Providing tactile feedback can be a challenge with the constraint of a relatively large lens. The Fig. 2: Touch-lens system interface diagram. haptic actuation and lens mounting features need to be carefully chosen to accomplish the desired wave propagation on a rigid spatial recognition is a new feature gaining popularity and curved surface. adding multi-stage touch sensing or the press- offers some unique challenges to the touch-lens. If the re- for-intent feature increases the complexity of the mechanical quirements are simple driver vs. passenger hand detection, a mounting by requiring detection of a slight pressure while main- projected capacitance solution may suffice. However, for more taining a mounting system suitable for haptic feedback. complex gestures and larger detection areas above the panel, IR LED reflection, or possibly IR camera technologies are war- Paul F. Weindorf is Display systems Technical Fellow at Visteon ranted. This solution requires the use of an Ir transmissive sur- -www.visteon.com face. Other technology used to recognize no-touch movements James. J. Kornacki is center stack electronics Global Platforms (such as ultrasound), may result in a decreased craftsmanship & hMI subsystems Manager at Visteon. level (visible microphone openings). www.electronics-eetimes.com Electronic Engineering Times Europe December 2012 17


EETE DECEMBER 2012
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