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 (Figure 1).
Figure 1: Touch-lens in integrated center control panel
Display interface requirement considerations for the touch-lens include functional, aesthetics, and performance & conformance categories. Figure 2 shows a representation of these interface requirements (green), enablers (yellow), and the key component (pink) of the system.
Figure 2: Touch-lens System Interface Diagram. For better resolution click here .
Addressing all of these considerations 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
- Performance & Conformance – display visibility, acceptable birefringence, head impact regulatory compliance, and environmental performance.
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 thickness of at least 2-2.5mm that impacts the selection of the touch technology.
Integrating touch sensing:
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. Technology 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.
Augmenting touch inputs:
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 haptic actuation and lens mounting features