A recent webinar by Radiant Vision Systems’ Optics Development Manager highlighted recent advancements in image quality assessment, which is required when integrating prescription lenses into augmented, mixed, and virtual reality (AR/MR/VR) devices.
Such techniques are becoming increasingly important in a market where the use of virtual technologies is becoming ever more widespread, and most customers require prescription lenses.
With the increasing use of AR, MR, and VR (collectively XR) appliances across multiple industries, current trends suggest that AR/MR appliances will take up a significantly bigger part of the current market.
With such significant growth in AR/MR users, multiple factors should be taken into account for user experience; among them is that a larger share of potential users need prescriptions to correct their eyesight.1
Over 4 billion people globally use prescription lenses, equalling roughly two-thirds of the worldwide population. Projections indicate that by 2050, half of the world’s population will be in need of some sort of prescription lens.2
Around 84 % of adults over the age of 45 use vision correction lenses, and the need for glasses in children has also considerably grown—approximately 40 % now need them. This equates to twice as many children requiring prescription lenses compared to the 1970s.
Therefore, manufacturers clearly need to take into account the development of tailored optical configurations for XR devices that are used instead of regular eyeglasses and for lenses that may be inserted into some devices to substitute prescriptions for glasses. These lenses could be developed via 3D printing and cold casting.3
Examining the imaging quality of AR/MR devices
The “Novel Testing Methods for AR/MR Devices and Smart Glasses with Vision Correction” webinar by Eric Eisenberg at the 2023 Photonics Spectra Optical Metrology Summit actually explored some of these issues, particularly focusing on the integration of prescription lenses into AR/MR devices. He also offered some novel solutions from Radiant Vision Systems in response to such issues.
Owing to his broad experience with optical technology and imaging, Eric Eisenberg has extensive knowledge of the technical considerations needed to properly incorporate optical technology in imaging systems. This article will summarize the key takeaways from this talk, which is available for free online from Photonics Spectra.
Issues linked to integrating prescription lenses into VR/AR/MR devices
Ophthalmologists prescribe lenses based on two key factors: spherical error, which can be either positive or negative, and cylindrical error, which corrects astigmatism—a condition where the eye focuses more effectively in one direction than another.
For spherical error, prescriptions typically provide a correction range of +6 to -6 diopters on the optical power scale for each assessment. In cases of astigmatism, corrections of two or more diopters can be prescribed as needed.
A typical vision prescription with a range of +6/-6 diopters for each measurement, out to 2 decimal places. Image Credit: Radiant Vision Systems
Prescriptions are given in 0.25 diopter increments for spherical correction and in 1/5-degree angular increments for astigmatism. Because these lenses are tailored to an individual’s unique eye physiology, each one is custom-made to address specific vision issues. This high level of variation creates a significant challenge when evaluating display system quality in XR devices that incorporate prescription lenses.3
An essential trait in proper quality inspection of AR/MR appliances is assessing the display accurately as a human wearer is able to see it. Device makers should make sure that the images displayed are sufficiently bright and are not blurred or distorted, among other visual quality requirements.
Factors that influence image quality include focal distance—the virtual distance from the wearer’s eyes where images are most sharply in focus.
Usually, a device’s optical system generates images at a focal distance suitable for individuals with “normal” vision who are not in need of prescription lenses. However, problems emerge when the optimal focus distance for a user with prescription glasses does not correspond with the device’s default setting.
For instance, if images are designed to be sharp at a virtual focus distance of two meters, they will seem blurry for users whose prescription lenses change focus in a different way. This discrepancy underscores the need to accommodate different focal distances to precisely measure an appliance’s image quality.3
So, how can an appliance be tested at all of the possible focal distances amid all of the other prescription vision variables?
A conventional method for prescription lens compensation is the “Brute Force” approach, which mechanically inserts reversed compensation optics to take into account the user’s corrective optics.
This approach, although direct, is complicated, and requires many lenses and moving parts. It therefore is extremely impractical for assessing the XR device image quality for multiple reasons.
The main challenge with the “Brute Force” approach is the lack of space to add extra optical lenses between the eye’s entrance pupil (its position inside the headset) and the device.
Additionally, manually adjusting the measurement system for each prescription is highly time-consuming, making it impractical for testing hundreds of thousands—or even millions—of devices that would require mechanical lens replacements.
A more efficient solution is to leverage existing optics and mechanics within the imaging system to automatically adjust for different prescriptions. Radiant Vision Systems has developed an innovative XR device testing solution that incorporates electronic lenses that are capable of making these adjustments seamlessly.3
A new approach to AR/MR image quality testing
Diopter (Spherical) compensation
Radiant’s XRE Lens, combined with TrueTest™ TT-ARVR Software, eliminates the need for multiple mechanically moving optical lenses by enabling electronic focus adjustment. With this system, small electrical changes allow for significant shifts in overall focus, streamlining the process and improving efficiency.
Spherical correction—used to address nearsightedness and farsightedness—is achieved by calibrating the imaging system’s focal distance “beyond infinity” using negative diopters. In AR/MR systems, the relationship between optical power and lens motor movement follows a linear pattern, allowing the internal microlens to be adjusted to a negative imaging power.
This adjustment is crucial because, while an XR device may display an image at infinity, prescription lenses alter the focal point, effectively shifting the image “past infinity.”
To compensate, the XRE Lens’s microlens focus can be adjusted accordingly. Unlike standard lenses, the XRE Lens has the unique capability to "focus beyond infinity," enabling diopter compensation through electronic adjustments.
This automated focal adjustment ensures precise image testing at various prescription strengths, allowing focus positions to be verified and iterated as needed. Additionally, software control maintains the integrity of modulation transfer function (MTF) measurements, ensuring accurate and reliable results.
Compensating for near-sighted optics by “focusing beyond infinity”, diverging the light rays to correct for near-sightenedss (negative diopters). Image Credit: Radiant Vision Systems
For example, when a 4-diopter lens was inserted into the device under test (DUT), the measurement results showed nearly identical contrast values for the modulation transfer function (MTF), despite differences in motor counts. The specific motor count at which the peak contrast occurs is not critical—as long as the peak value remains consistent.
Based on these findings, Eric Eisenberg is confident that this method can effectively accommodate the full +6 to -6 diopter range for spherical corrective lenses.
Astigmatism compensation
With astigmatism, the required optical compensation varies across different axes, necessitating a cylindrical component to properly focus the eyes. The astigmatism angle can range from 0 to 90 degrees, meaning the pattern used to evaluate a device’s focus quality must be aligned with the astigmatic axis of the prescribed lenses.
By adjusting the software’s pattern generator, random angles can be entered for contrast characterization, allowing the system to calculate the modulation transfer function (MTF) based on the orientation of these lines.
If the prescription is known, the system can be programmed accordingly. If the prescription is unknown, it can cycle through a range of values to determine the correct prescription. Once the test pattern aligns with the astigmatic axis, the resulting MTF contrast closely matches what would be observed without prescription lenses, ensuring accurate assessment.
Watch the webinar to learn more about these solutions
Radiant Vision Systems has offered a new and effective solution for the imaging assessment of AR/MR devices integrated with prescription lenses, enabling both fast and precise assessment.
Automation is essential for these new advancements, and Radiant Vision Systems can provide advanced abilities for both manufacturing and testing XR devices. For a more comprehensive explanation of this approach, watch the following webinar online for free.
References and further reading
- Ahmet Güzel, Beyazian, J., Praneeth Chakravarthula and Kaan Akşit (2022). ChromaCorrect: Prescription Correction in Virtual Reality Headsets through Perceptual Guidance. (online) https://doi.org/10.1364/opticaopen.21912831.
- Sadovsky, G. (2023). Eyewear Industry Statistics. (online) Overnight Glasses. Available at: https://www.overnightglasses.com/eyewear-industry-statistics/.
- Radiant Vision Systems (2023). Novel Method of Prescription Vision Compensation to Measure AR/MR Devices and Smart Glasses | Radiant Vision Systems. [online] Radiant Vision Systems. Available at: https://www.radiantvisionsystems.com/learn/webinars/novel-method-prescription-vision-compensation-measure-ar/mr-devices-and-smart (Accessed 6 Mar. 2025).
About Radiant Vision Systems
World leaders in manufacturing rely on Radiant Vision Systems for test and measurement solutions that ensure quality, reduce costs, and improve efficiencies. Based in Redmond, WA, Radiant Vision Systems has proven production experience with thousands of cameras testing millions of devices worldwide. We approach each application with a wider range of solution options, a global base of experience, and a depth of understanding that enable us to keep raising the benchmarks for practical performance.
Radiant Vision Systems engineers advanced imaging systems to critically evaluate light, color, manufacturing integrity, and surface quality of illuminated displays and device assemblies. Radiant products include TrueTest™ Automated Visual Inspection systems for measurement and control, ProMetric® Imaging Colorimeters and Photometers, Source Imaging Goniometer® systems, lenses for measuring AR/VR/MR/XR devices, intensity of near-infrared (NIR) emitters, and view angle performance of displays. We also offer the most extensive machine vision software tool library for production-level measurement and control. We back our systems with outstanding consultative technical support, ensuring that our clients enjoy and leverage all the value built into their systems.
In addition to its Redmond headquarters, Radiant Vision Systems has direct offices in Cupertino, CA and Novi, MI; Shanghai and Shenzhen in Mainland China; Taiwan; and Seongnam, South Korea, along with production facilities in Redmond; Suzhou, China; and Vietnam. The company is represented worldwide by a combination of direct and indirect distribution channels. Radiant has been a part of Konica Minolta’s Sensing Business Unit since August 2015.
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