Blog

OLED Plus HMI, the “Must Win” Race

Background

Industry analysts estimate the OLED (Organic LED) display market size at more than $32B USD in 2019, with some projections showing the market growing to over $200B by 2027 (more than 20% growth during the period). The value in shifting to OLED over LCD is strong including the super fast response of the display, vivid colors, crisp high contrast images, and a thinner stack-up. OLED is also expected to launch aggressive growth in a variety of new phone and laptop form factors using foldable and/or wrap-around displays. While OLED phone shipments now surpass LCD based phones, leading manufacturers have faced significant performance and manufacturing challenges involving the integration of touch sensor into the touch/display module. These challenges include an increased overall thickness of the OLED stack-up and increased noise as well as higher capacitance due to the close proximity of the sensor to the OLED drive layers. All of these issues result in significant challenges to existing voltage-mode, scanning based touch controllers. Scaling such solutions for high speed response and laptop display sizes is extremely difficult, if not impossible, for existing touch controller technology. Substantial benefits are offered by touch controllers using current-mode ADC’s which use low voltages to deliver instantaneous and high precision data even with the high noise, high capacitance of on-cell OLED.

The PC industry is now faced with real and significant technical challenges that threaten to block or at least slow OLED adoption for tablets and notebooks. The value created by the smart phone transition to OLED is massive. Similarly, the PC OEM that solves these touch integration issues and delivers the best HMI (Human Machine Interface) utilizing OLEDs for Tablets, Laptops, and All-in-Ones, will gain a significant advantage and win value that comes with improving the client experience. HMI support along with management of high-fidelity sensing data will mark this transition to OLED displays which will prove much higher value than the mere revenues from the device sales. Application of AI processing for determination of user intent and the leveraging of HMI for exceptional experiences is the new MUST WIN race. A current-mode ADC based touch controller can deliver significantly better sensing data at lower voltages. Better data is essential for the ability of AI processing to deliver next generation HMI experiences. OLED optics combined with exceptional HMI support represents a tipping point for the PC industry… the new MUST WIN race.

PC OEMs have experimented with OLED in their product lines by building expensive high-end laptops, but without the high-end HMI interfaces supporting both touch and pen. Efforts to build thin foldables with touch/pen-based OLED displays have not yet been successful because they have had so many compromises so as to relegate these systems to the category of “curiosities”.

Some OEMs will wait for the display manufacturers to design their own HMI solutions into their display products thereby surrendering the chance of owning the differentiation and value which comes with control of the HMI experience. Others have recognized the tipping point for the next generation of computing devices is tied to OLED, HMI, and intuitive experiences that are the result of higher-fidelity sensing data. Display Manufacturer, or PC OEM, whoever wins this race is likely to cause significant disruption in the traditional PC markets.

OLED

OLED based systems hold the promise of transitioning the PC industry to a new generation of foldable, rollable, wearable, devices that deliver a thinner, softer, and lighter compute experience to these larger devices. The promise is within reach including higher contrast optics, on flexible screens with better video graphics. Add to this an HMI with faster touch response, intuitive skins on all sides, and a more natural handwriting performance and the market will tip. Unfortunately, the richer HMI experiences is not simply a matter of repurposing the current generation of touch controllers from LCD to OLED. This approach is holding back OLED deployments.

HMI Challenges

Customers expect all screens to be capable of responsive, predictable interactions regardless of display type or size. Phone size OLED displays with curved edges that support both pen and touch are an excellent first step however, far better SNR (signal-to-noise-ratio) will be required to achieve the OLED promise (including flexible screens) to a broad range of display sizes. As the PC industry maps its transition to OLED, the roadblocks being faced cannot be resolved with the existing threshold-based voltage mode approach to PCAP touch sensing. An approach with far better SNR performance is required. Some of the road blocks include:

  • Larger displays mean longer channel lengths for sensing a change in voltage for touch and pen over the surface of an OLED. Voltage based sensing systems require more charge and longer scan times based on the resistance and capacitive loads for a laptop vs. a phone size screen.
  • Longer lines mean higher total resistance channels. While OEMs may choose to compromise by using low resistance materials, this reduces the optical advantage an OLED stack-up and can increase cost.
  • Thinner stack-ups mean the touch sensor layer is closer to and receives dramatically more noise from the OLED drive layers used by the continuously operating OLED display controller. This increases significantly the need for a larger touch voltage to get the signal above the noise. High voltage signals increase power consumption and interfere with the optical performance of the OLED.
  • Deposition processes for building on-cell sensors place these touch sensing conductors just microns off the OLED top anode/cathode layer. The close proximity of these conductive layers adds a massive capacitive load to the touch controller which slows the charging and scanning of the touch signal and further degrades the touch performance. Solutions are costly and generally add thickness to the stack-up.
  • Traditional touch and pen systems report at rates of 133Hz with hopes of moving to 266Hz but are not adequate for expected gaming response speeds. High speed displays with high performance graphics are wasted if the interactive experience is ruined by long latency in the pipeline, thus compromising with touch and pen lag. Poor haptics feedback can also be a direct result of slower sensing speeds.
  • Expensive rigid frames to manage the movement of the touch sensor layers have been the hallmark of threshold-based voltage mode touch systems. Any flex or movement of the screen causes spikes of noise or significant changes in capacitance, these dynamic changes interfere with the ability of traditional PCAP touch controllers to reliably process touches because the need to continuously adapt. This requires expensive hinge designs that lock the device into specific configurations as a requirement of OLED based foldable systems before touch will operate correctly.
  • Touch controllers are dictating expensive and frequent design changes to OLED systems due to the trial and error approach of tuning a scan based system for production. Tight tolerances requiring impedance uniformity on every row and column, every trace, plus emissions management of every frequency source in the system requires tuning and re-tuning to protect the touch performance. The physics of tuning todays voltage mode touch systems drives up cost, increases risk, and delays launch of OLED devices.

HMI Problem Solved

SigmaSense® is pioneering a massive industry shift away from traditional voltage-mode touch sensing to current-mode ADCs using ultra-low voltages, with the ability to simultaneously drive, sense, and respond so operations are unified with the OLED screen regardless of size. The shift to current-mode ADCs means no more scanning dependencies, with voltage thresholds to detect a touch. Its unique SigmaVision® technology uses current-mode sensing to image the entire display in order to sense touch, pressure, high hover, touch through thick gloves and even detecting non-conductive objects like game pieces or wooden chopsticks. SigmaSense® is delivering sensing with 100 to 1000 times better SNR by moving away from traditional touch technologies. Current-mode ADCs provide instantaneous sensing results unincumbered by traditional RC timing constraints due to charge times and scan requirements.

  • Long line rows and columns ALL report at the same time regardless of display size and can use voltages that are about 1/100th that of voltage-mode touch systems. No more scanning of rows and columns (proven support on displays from 6.5 inches up to 100 inches).
  • High resistance channel lines provide for superior OLED optical performance and lower cost sensors. With the use of SigmaSense® technology the high resistance channels act as a low pass filter helping block environmental noise and further improving SNR performance (even with line resistance greater than 400 Ohms/square).
  • Ultra-low voltage is used to sense touch on a thin OLED stack allowing SigmaSense® to operate in most cases below 0.5V so the OLED video processing is never harmed by the signal. The low voltage signal senses continuously with high SNR during the operation of the OLED.
  • Sensor design can now be optimized for flexibility and cost since current-mode ADCs are much less impacted by capacitive loads associated with close proximity to the OLED anode/cathode layer. This enables thinner less expensive sensor designs.
  • The physics of current mode sensing allow for much faster report rates (300Hz+) of all rows and columns concurrently. The capacitive imaging approach delivers high-fidelity data that is an ideal application of AI processing for superior interactive experiences. Gaming and handwriting applications also significantly improve with the higher report rates for strong differentiation.
  • The movement due to folding and stretching of the conductors on the screen changes resistance creating threshold differences that are easily managed if current is being sensed instead of voltage. High resistance polymer conductors used in small screens (like watches) can now be used in screens up to 86 inches. These materials solve the folding and hinge design issues that are so costly today.
  • Current mode sensing allows simple design options that no longer require cycle after cycle of engineering time to do the tuning. Superior noise immunity delivers more than 100X better SNR so design tolerances for noise immunity from display to radios and power supplies are greatly simplified.

Capacitive Imaging

SigmaSense® delivers the breakthrough that is necessary for transition to OLED based devices by solving the unique problems that are created by the thinner OLED structure and continuous noise during operation. Combine the benefits of OLED displays with the unique SigmaSense® advantages for capacitive sensing through high resistance polymer materials (while folding) and the HMI design issues are greatly simplified.

Conclusions

Current mode ADCs will replace the current generation touch controllers with faster high-fidelity data capture at the edge between analog and digital domains. SigmaSense® provides ultra-low voltage capacitive imaging with the ability to sense what has been impossible until now.

The result is OLED based systems with new features, and new interactive experiences delivered with greatly simplified designs. As the next generation of client computing emerges, HMI and intelligent application of high-fidelity sensing data will be the reason some win while others lose.

OLED devices without next generation HMI solutions cannot fulfill the promise of what OLED is capable of delivering. The first team to deliver OLED combined with leadership HMI features is set to move the PC Industry across the tipping point to all new and more creative compute experiences.

SigmaSense® Company Summary

SigmaSense®, the global leader in touch sensing performance, is ushering in the next generation of user experiences to a wide range of products. SigmaDrive® a unique current mode delta sigma technology is providing from 100 to 1000 times superior signal-to-noise (SNR) capability compared to the industry today. Because each touch sensor channel has a dedicated sigma-delta modulator and are all concurrently driven and sensed using a digital narrow band filter, an extremely high SNR is achieved even while using a very low drive voltage. SigmaVision® capacitive imaging technology further extends the user experience by providing a superior touch and touchless interactive experience for displays. This is directly solving the challenges that are being faced by the migration of mobile and large devices to OLED based display making them flexible, responsive and engaging.