Posted in | Lenses

Near-Eye Display Testing with an AR/VR Lens

The AR/VR lens from Radiant Vision Systems has an exclusive optical design specifically developed for quantifying near-eye displays (NEDs), like those incorporated into augmented (AR), mixed (MR), or virtual reality (VR) headsets.

The lens design mimics the size, field of view, and position of the human eye. The aperture of the AR/VR lens is different from alternative lens options, where the aperture is situated inside the lens. Instead, it is situated in the front of the lens, making it possible to position the entrance pupil of the imaging system inside the NED headsets, to observe head-mounted displays (HMDs) at the same place as the human eye.

Evaluates the Full Display Field of View Experienced by Human Users

Displays—viewed close to the eye, like those in VR/AR devices—create immersive virtual experiences. But display defects also get amplified since display images are amplified to fill a user’s field of view. Problems with uniformity of color and brightness, cloudiness, line defects, dead pixels, and image position turn out to be more evident to the user, whose eyes are just centimeters away from display screens.

In cases like these, display quality testing is a crucial step for controlling product quality. Test and measurement solutions for assessing NED quality comprise photometric imaging systems coupled with software for measuring and analyzing chromaticity and luminance.

But conventional optical components that quantify displays like smartphones and televisions do not include design considerations for simulating the view of visual input of the human eye at the distances needed for head-mounted display devices.

The Radiant Vision Systems AR/VR lens—exclusively designed for display quality measurement in NED headsets—comprises aperture properties that replicate the approximate position, size, and field of view of the human eye. Moreover, with the aperture located at the front of the lens, the attached imaging system can capture the full field of view (FOV) of the display (up to 120° horizontal, encompassing approximate human binocular FOV) without any hindrance by the lens hardware.

In addition, the aperture size of 3.6 mm corresponds with the size of a human entrance pupil, enabling displays to be quantified under the same settings as they are seen by a human observer. This guarantees that all aspects of the display perceptible to the user are completely quantified to ensure the targeted experience.

Competitive measurement systems using standard optical accessories (like a 35-mm lens) cannot simulate the visual experience of the human observer because the aperture is built within the lens enclosure. This restricts the display’s full angular field of view to be captured without obstruction by the NED headset hardware (the eye lens’ frames).

The effect is just like visualizing a scene via a knot hole in a fence—the FOV can be observed beyond the fence when the eye is positioned at the hole; when the eye shifts away from the hole, the view becomes obstructed by the fence’s edges.

Mount to ProMetric® Photometers and Colorimeters

The AR/VR lens is essentially an optional mounting accessory for ProMetric® Y Imaging Photometer or ProMetric® I Imaging Colorimeter from Radiant Vision Systems. The colorimeter is attached with the help of a custom mounting bracket, thus ensuring stability during vibration or movement.

When a lens is directly mounted to a ProMetric® imaging colorimeter or photometer, the AR/VR lens provides the most efficient method of quantifying NEDs as a compact, turnkey lens/camera solution that does not need extensive setup and integration time, expertise, or equipment.

The AR/VR lens can be effortlessly removed and substituted with normal lenses for further display measurement applications, like testing displays on the production line or beyond the headset equipment.

Complete Toolset for AR/VR Display Measurement

A comparison between an AR/VR Lens and a Standard Lens

The AR/VR lens—coupled with a Radiant ProMetric® imaging colorimeter or photometer—captures high-resolution images of displays for sub-pixel and pixel measurements to identify anomalies and defects in projection displays, OLED, LCD, and LED.

The Radiant TrueTest™ Software also offers the leading display test algorithms, with the potential to sequence tests for quick evaluation of all pertinent display properties within seconds, applying chosen tests to one image captured by the camera. Typical tests in the TrueTest™ Software comprise uniformity, contrast, chromaticity, luminance, line defects, pixel, mura (blemishes), etc.

Unique tests for AR/VR display analysis are given below:

  • Distortion of images (for distortion characterization)
  • The modulation transfer function (MTF) to assess the clarity of images, based on Slant Edge Contrast ISO 12233
  • Retention/sticking of images
  • Spatial x,y position reported in degrees (°)
  • Factory distortion calibration of the lens solution to standardize wide-field-of-view images for testing

Through this comprehensive Radiant solution configured for precise application requirements, manufacturers can achieve an efficient measurement process with the advantage of a sole provider with end-to-end support.

Key Features and Highlights of the AR/VR Lens

  • Aperture placed at the front of the lens to replicate the entrance pupil of the human eye, capturing FOV of HMD projections via the headset viewing lenses
  • Precise and reliable measurement of the display chromaticity and luminance
  • FOV of the lens (120° horizontal) encompasses approximate FOV of binocular human vision
  • Aperture size (3.6 mm) replicates the pupil size of the human eye
  • Easily coupled with ProMetric® imaging photometers or colorimeters
  • Designed to be placed at the location of eye relief
  • User-friendly measurement control and analysis software
  • Combination of high performance, low cost, and flexibility developed for research and development and quality assurance

All ProMetric® camera solutions from Radiant Vision Systems are available with ProMetric® Software—a robust software suite that enables data acquisition, intuitive camera setup and control, and image analysis.

Elaborate display functions and data analysis are also supported, such as radar plots, cross-section graphs, isometric plots, CIE color plots, and bitmaps. For further measurement and test sequencing options, the TrueTest™ Software provides the complete range of Radiant display measurement capability.

Typical Applications

The AR/VR lens is the first product to allow the assessment of the complete display visible to the human eye via the AR/VR headsets. High-resolution imaging is provided by the camera/lens to address both in-line and off-line applications:

  • Characterization as well as quality control for devices in research and development, and production
  • Measurement of near-eye displays; suitable for AR, VR, and MR headsets
  • Test and measurement of chromaticity, luminance, MTF, contrast, image retention/sticking, image distortion, and x,y image position

Near-Eye Display Testing with an AR/VR Lens

Evaluates the Full Display Field of View Experienced by Human Users
Mount to ProMetric Photometers and Colorimeters
Wide-field-of-view images taken by a camera/lens solution before factory distortion calibration. Distortion calibration of each system ensures accurate spatial data is acquired by normalizing the lens effects in wide-field-of-view images.
Wide-field-of-view images taken by a camera/lens solution after factory distortion calibration. Distortion calibration of each system ensures accurate spatial data is acquired by normalizing the lens effects in wide-field-of-view images.

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