Authors:
[1] Dr. Kedar Sathaye, Product Manager Light & Display at Konica Minolta Sensing Europe B.V.
[2] Dr. Valentyn Volkov, co-founder of XPANCEO
The market for image display devices is rapidly evolving, with innovations ranging from advanced screen technologies in smartphones and TVs to more sophisticated solutions like augmented reality (AR) glasses and virtual reality (VR) headsets, such as the Apple Vision Pro. The XR market alone is projected to reach an impressive $1,913.7 billion by 2032, with a growth rate of 39.2% from 2024 to 2032. There’s an increasing focus on making these devices more wearable and user-friendly. Achieving this goal, however, presents significant challenges due to the limitations of current technologies.
Wearable devices, particularly in the AR and VR sectors, often face critical performance issues. For example, AR glasses and VR headsets frequently lack sufficient brightness, have limited battery life, and often end up being bulky due to the need for larger batteries. These issues can lead to overheating and reduced field of view, decreasing the practicality of these devices for long-term use. This is driving the industry to innovate and develop new devices that overcome these challenges. However, this rapid development invites another problem: the lack of comprehensive test solutions to ensure that these new devices meet the required standards for quality, safety, and performance.
In response to this gap, Konica Minolta and XPANCEO have partnered to meet the growing demand for contemporary test solutions.
AR Smart Contact Lenses
XPANCEO is a deep-tech company pioneering smart contact lenses, a new frontier in wearable technology that it envisions as the next generation of computing. These lenses aim to solve the problems of current wearable technology by integrating various traditional device functions into a single interface that is weightless and as natural to the wearer as their own vision. Beyond applications such as health monitoring and enhanced vision, a key focus for XPANCEO is image projection. The company has already succeeded in developing a smart contact lens with a display that significantly outperforms standard solutions.
By reducing the resolution in the peripheral vision area—where the eye does not require high resolution—the load on the video controller is minimized, allowing for much smaller packaging. Additionally, the brightness loss from the display to the eye is reduced threefold, and the total power consumption is expected to be only 1-3 µW, which is 100-300 times less than comparable AR glasses.
However, this technological advancement raises new questions about testing and quality assurance, as there are currently no ready-to-go solutions on the market.
Image Quality Testing
To help manufacturers like XPANCEO ensure quality of the display, Radiant’s AR/VR Lens paired with a ProMetric® Imaging Photometer or Colorimeter provides unique optics engineered for measuring near eye displays (NEDs), such as those integrated into virtual, mixed, and augmented reality headsets. The innovative new geometry of the lens design simulates the size, position, and binocular field of view of the human eye. Unlike traditional lenses where the aperture is located inside the lens, the aperture of the AR/VR Lens is located on the front of the lens to enable the connected imaging system to replicate the location of the human eye in an AR/VR device headset and capture the entire FOV available to the user.
Radiant developed an AR/VR Lens to address the unique challenges of qualifying integrated NEDs under the same conditions as they are visualized by human users. The AR/VR Lens is designed to be paired with high-resolution imaging photometers and colorimeters, 16-megapixel and higher resolutions. By capturing displays at this detail, the measurement system can evaluate the entire display FOV at once with the precision to capture any defects that might be noticeable to the human eye.
Radiant’s AR/VR display test solution is specially designed for in-headset display measurement. What separates the AR/VR Lens from other optical components is the lens’s ability to replicate the FOV and entrance pupil of human vision. The AR/VR Lens product specifications include:
Aperture (entrance pupil) located at the front of the lens.
3.6 mm aperture size. The average pupil will contract to 1.5 mm in diameter in bright light and dilate to 8 mm in diameter in darkness. Radiant uses 3.6 mm for two reasons: 1) it is in the mid-range of pupil dilation; 2) the 3.6 mm aperture allows a high MTF for the lens.
Wide FOV to 120° (±60°) horizontal.
Importance of Calibration
Each Radiant AR/VR camera/lens system is factory calibrated to ensure the most accurate images for absolute light and color analysis. Calibration processes include factory distortion calibration to remove lensing effects of the wide-FOV lens, ensuring accurate spatial analysis of the display by the camera software. When measuring displays using a wide-FOV lens, the image captured by the lens may appear distorted as shown in figure below.
Because the AR/VR solution uses a fisheye lens, an uncalibrated image exhibits barrel distortion. Radiant’s camera/lens solution is calibrated to process out distortion effects before applying display tests. This ensures accuracy of spatial measurements to detect defects where they occur on the display.
Software Solution
Radiant TrueTest™ Automated Visual Inspection Software applies analyses to all images captured by Radiant’s AR/VR measurement solution. This platform includes a suite of display tests with standard tests for luminance, chromaticity, contrast, uniformity, and defects like dead pixels and lines. In addition, unique tests for AR/VR projections are available in the pre-configured TT-ARVR™ software module.
Some examples of TT-ARVR software analyses are shown in Figures 14-16 below. These analyses are performed on the AR/VR display to test the manufacturing specifications of the AR/VR device. These specifications can also be published for consumer use (for instance, on an AR/VR headset specification sheet) to help them evaluate the device and compare with competitive products.
Uniformity analysis as shown in figure below determines areas of low or high luminance across the display, which may indicate a defect in the display. This analysis can also be used to characterize the uniformity against design specifications.
A checkerboard contrast analysis as shown in figure below is performed by projecting a checkerboard pattern on the display within the AR/VR headset. Once the pattern is imaged by the AR/VR test system, the checkerboard contrast test evaluates luminance levels in the image to determine the display system’s ability to project distinct light and dark values - a performance parameter that can be indicated on a specification sheet.
Customized Testing
Radiant Vision Systems, a Konica Minolta Company that focuses on solutions that can be used across various applications, has partnered with XPANCEO to develop a custom testing system that measures critical parameters for these emerging devices:
Field of View: The XR smart contact lens is designed to allow users to see images from any angle, requiring precise measurements to ensure the gradual improvement of this parameter.
Brightness of Virtual Images: While traditional light bulbs can be easily quantified, virtual images provide a subjective experience that necessitates an objective testing system. This is particularly important given strict medical guidelines on image brightness to prevent damage to the human eye.
Contrast: This measures how clearly an image stands out from the background and is crucial for comfortable and safe viewing. It should remain stable regardless of the brightness of the environment.
Adaptation to Weather Conditions: The brightness of virtual images needs to adjust to different weather conditions, similar to how phone screens adapt, without causing excessive brightness that could blind the user if they look directly at the sun.
The gradient of Intensity Across the Field: For optical reasons, virtual images have varying brightness, especially at the edges. Accurate measurement of this parameter is essential for correcting the image when it’s recorded for projection.
Line Sharpness: This parameter ensures that fine lines and details in the image are clear and easy for the user to see.
These advancements in testing are not only applicable to smart contact lenses but could revolutionize quality assurance in a variety of fields. Though the fully realized smart lens is still in the research and development stage, the technology behind it holds promise for broader applications in the industry, offering a significant opportunity for further development and standardization in wearable tech testing.
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