From its beginning Varjo positioned itself as the leader of VR head-mounted displays megapixel race. Their “human-eye resolution” VR-1 truly shows more detail than any other existing HMD.
However, just offering a high pixel count does not mean the user will be able to see a crisp and clean picture through the HMD optics, and in fact, it is the optics which present a display quality bottleneck. In a head-mounted display there are severe design constraints especially in making the optics light weight and fit in a tight space. Those constraints lead to a compromised optical performance, resulting in color fringing and blur. Moreover, any movement of the eye pupil, which itself constitutes a lens element, makes the entire optical system quite different from the original optical design, so the blur and color fringing get even stronger as the eye looks off the optical axis.
Almalence Digital Lens is a computational lens aberrations correction solution which overcomes these limitations by compensating the aberrations of an HMD optics. It does the job of a corrective lens element which dynamically adjusts its properties depending on the eye pupil position. We were eager to check how that technology can improve picture clarity of the highest resolution HMD.
Note 1: This testing was performed by Almalence independently from Varjo. The Digital Lens test was implemented as a Unity application using public API.
Note 2: This is the very first testing, definitely showing sub-optimal results. We see a clear way to further improve the image clarity with the given headset.
We used a construction drawing as a test picture as it clearly demonstrates how the insufficient apparent resolution and clarity limit the VR usability.
To take the images within the HMD, we used our camera system with our eye imitator, allowing to capture what a human eye would see.
In the first example the eye looks about 10 degrees off the center. The left part of the gaze area falls onto the high resolution “focus display”, the right part falls onto the lower resolution “context display”
Move the slider left/right to see the difference. Left: Varjo VR-1 as is; Right: VR-1 with Digital Lens. Despite the high display pixel count, the picture does not look very clear. One can even start feeling sick when trying to read the numbers. The very same display with the Digital Lens delivers much clearer and readable picture.
In the next example the eye looks straight at the center, along the optical axis – the ideal case in which the HMD delivers its highest possible picture quality. The gaze area is completely over the focus display. Even in that case the Digital Lens shows a noticeable improvement:
Left: Varjo VR-1 as is; Right: VR-1 with the Digital Lens. Same display, but more legible text and crisper lines.
The beauty of the Digital Lens solution is that it is a pure computational technique, adding no extra size, weight or mechanical complexity to the device.
As mentioned above, those are very first tests, more to
follow. However the tests already prove that the Digital Lens is an indispensable
technology for high-end VR headsets, allowing to harness the full potential of
high display pixel count and density.