The global automobile touchscreen industry has skyrocketed since it first started in the 1980s, which saw the very first touchscreen panels appearing in cars and vehicles. Today, the industry has continued its expansion of display panel integration into dashboards and other locations within cars.
The predominant technology for automotive screens has historically been LCDs – that is until the emergence of OLED display technology offered the appealing prospect of higher brightness for improved visibility in all ambient light conditions.
New design possibilities were opened by the flexibility of OLED panels - offering curved displays and enabling manufacturers to bring their creativity to the forefront, integrating displays into a wider variety of spaces in the automobile. However, it must be noted that these OLED displays have had issues regarding the durability requirements of an automotive environment.
As we all know, vehicle components are subjected to extremes in terms of direct sunlight, temperature, vibration and humidity. These stumbling blocks have meant that OLED has not yet made significant inroads into replacing LCDs, which remain the mainstream display of the automotive industry today.
A few of the potential locations for displays within an automobile include the dashboard, center stack, HUD, passenger entertainment displays, camera mirror system (CMS) integrations, and more. Image Credit: Radiant Vision Systems
Automotive Applications: The Benefits of MicroLEDs
The improved brightness and flexibility of OLED are promised by microLED displays – offering the prospect of greater reliability, which catches the attention of automakers. MicroLEDs offer multiple advantages for automotive display applications, including:
- High contrast and luminance
- High pixel density (pixels per inch, or PPI)
- Wide color gamut
- Flexibility
- Low power usage
- Stability at a wide range of operating temperatures
MicroLED displays are also expected to reach commercialization in the automotive industry as soon as 2022-2023.1 For instance, the new microLED TFT automotive displays from AUO include a 9.4” curved screen built on a flexible plastic LTPS backplane.
AUO microLED displays at SID DW 2020
Video Credit: AUO
Indeed, it is expected that microLEDs will catch on faster within the automotive industry than they have done in the mass consumer market.
When it comes to consumer products, high fabrication costs remain an obstacle for many, which has seen the range of many microLED products thus far limited to high-end devices in the fields of television, AR/VR headset, and smartwatches.
However, microLED displays add a relatively small incremental price that can be more easily absorbed into the overall vehicle cost, as they are simply one of many components of an automobile.
Next-Generation Automotive HUD: Enabled by MicroLEDs
When it comes to the newest class of automotive head-up displays (HUDs), MicroLED technology is particularly appealing for manufacturers and consumers alike “since it is the only display technology which could offer the high enough brightness to yield the contrast necessary to clearly see an image against a bright sun-lit background (including sun shining right through the windshield) and wide operation temperatures to withstand weather swings from bitter cold in winters to scorching heat in summers.”2
The driver can track key information like speed and navigation while keeping their eyes on the road, thanks to the HUD's ability to project semi-transparent virtual images into a driver’s field of view.
Using either a transparent display screen (combiner) installed on the dashboard or simply a reflective film applied to the interior surface of a car’s windshield, these images can be projected to a convenient spot in the driver’s eyeline.
Combiners are quickly being replaced by windshield HUDs - particularly with the design and rollout of AR-HUD (augmented-reality-HUD) systems. AR HUDs project across wider fields of view, using more of the windshield for the display — and enabling images to integrate more dynamically with objects in the exterior environment at a greater range of virtual image distances.3
Plessey AR-Vµ microLED Display - Automotive HUD Application
Plessy demonstrates a microLED HUD display. Video Credit: Plessy
MicroLED displays have a bright future in the automotive industry, with the automotive HUD market projected to grow at a 22% CAGR, reaching $5.7 billion globally by 2030.4
Uniformity: A MicroLED Quality Challenge
Product manufacturers must be able to consistently deliver the quality that consumers expect in order to achieve market success. Each microLED is driven independently to produce its own light and is thus termed an ‘individual emitter’.
This enables the wide color gamut and contrast that appeals to manufacturers but also means that microLEDs can suffer from a real variability in brightness and color. This can therefore result in a non-uniform presentation that can render the displays unusable (unsalable).
As each microLED is usually a monochromatic subpixel (red, green, or blue), the output of which is combined with other subpixels to generate the overall brightness and color of a single display pixel, this variability is compounded.
This nonconformity at both the pixel and subpixel level manifests as a non-uniform appearance across the display, which can result in a very low yield of acceptable displays, a rejection of expensive components, or expensive rework.
MicroLED must deliver a flawless consumer experience, including uniform brightness and color appearance, for their display devices to achieve mass-market success. Buyer satisfaction can be easily risked by things like defects, dead pixels, variations in luminance or chromaticity and any other irregularities – which can ultimately hurt brand reputation.
Low yields and high production costs will impede the viability of microLED display technologies for market commercialization and mass production if these issues cannot be addressed and corrected at the component level.
MicroLED manufacturers must have a rigorous inspection process in order to address this challenge. Manufacturers can also employ systems that apply corrections to each emitter because microLEDs can be driven independently – thus improving display appearance without the need for rework.
An inspection system from Radiant Vision Systems that facilitates measurement and correction at the pixel and subpixel level is one novel solution that is being chosen by leading microLED innovators. Radiant assists manufacturers in ensuring quality products while increasing yields by guaranteeing that uniformity issues are addressed in production.
A microLED display before correction (left), and after the correction process—called demura—has been applied (right), resulting in a uniform appearance. (Image Credit: Jasper Display)
Radiant Solutions for MicroLED Inspection
A range of methods and solutions are offered by Radiant to address issues of imaging precision at critical points within the microLED fabrication process.
A ProMetric® Imaging Photometer or Colorimeter and TrueTest™ Software can be used with the company’s Microscope Lens to magnify microLED subpixels at extreme detail in a measurement image to provide wafer-level inspection of microLED chips.
Radiant has designed and developed two core methods for panel-level inspection that greatly improve the ability of an imaging system to isolate and measure increasingly small subpixels in increasingly high-resolution displays: a “fractional pixel” method and a “spaced pixel” method. Proprietary algorithms and analysis techniques applied via TrueTest are relied upon by both of these methods.
Radiant provides unique hardware and software solutions for pixel- and subpixel-level inspection at each stage of quality inspection during the microLED fabrication process, at the wafer stage inspecting individual chips, and at the panel stage following mass transfer and assembly. Image Credit: ALLOS Semiconductors
References
- Han, S. and Huang, A., “Automotive micro LED display commercialization expected in 2-3 years”, Digitimes, April 23, 2020.
- MicroLED Market Opportunities 2018-2027, N-Tech Research, July 10, 2018
- Chen, Y., “HUDs with LED and Laser Light to Become a Trend in Automotive Application”, LEDinside, October 25, 2019.
- Automotive Head-up Display Market, Transparency Market Research, July 13, 2020.
This information has been sourced, reviewed and adapted from materials provided by Radiant Vision Systems.
For more information on this source, please visit Radiant Vision Systems.