We learned last week that PSVR 2 will use Fresnel lenses, which have many advantages over traditional lenses, but also have one big drawback: god rays. However, Sony may have a trick up its sleeve that could give the headset’s Fresnel lenses a big advantage over the competition.
As we explained last week with the PSVR 2 lenses reveal, all major consumer VR headsets on the market have switched to Fresnel lenses, but unfortunately they have one major downside, which is ‘god rays’. . This is a visual artifact that is particularly prominent with high contrast elements (like white text on a black background) that appear to show streaks of light radiating outward from the center of the lens. This is a lens related issue; no matter what resolution you build into the screen or what type of screen you use, the image will always be negatively affected by the divine rays.
The industry as a whole has leaned towards Fresnel lenses apparently because they offer greater flexibility for lightweight and compact optical designs. High-end optical systems (like the lens of a DSLR) often stack multiple lens elements in a row to achieve the desired optical characteristics, but this has largely been avoided for VR headsets due to cost, the additional complexity and size that can come with multi-element optics.
Are we doomed forever to experience the divine rays in VR headsets with Fresnel lenses? Maybe not. And the PlayStation 2 could be the first headset to truly fix the problem.
A patent granted to Sony in 2020 proposes a “method of manufacturing the Fresnel lens which can suppress [god rays] […].”
The patent describes adding a “light absorbing portion” to the surfaces of the Fresnel lens that does not actually contribute to the overall shape of the lens (the backside of the ridges). This would, in theory, reduce the god rays by preventing light from being scattered through those parts of the lens. The patent shows several arrangements for the light absorbing part, both on the surface of the lens and integrated inside it.
If you’ve ever seen a Fresnel lens in a modern VR headset, you know how tiny the lens edges can be. Place light absorbing material alone on parts of the lens that are unwanted would naturally be difficult.
Sony’s patent offers several different methods of making such a lens. One is to apply a “mask” (which blocks light) over the entire surface of the lens and then, using some sort of exposure technique, remove only the part where the light should to pass.
Another method suggests starting with the light-absorbing material already shaped, then forming the lens around it so that the ridges line up perfectly with the light-absorbing structure.
It’s an interesting idea and, to our knowledge, not yet used in a VR headset.
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As always, big companies like Sony file lots of patents and many of them never become products. It is unclear whether the methods described are even practical for mass manufacturing. So it’s hard to say if this could end up in PSVR 2, but the option is on the table.
At a minimum, we at least know that Sony filed the patent with VR headsets in mind. While this patent could easily apply to the company’s many other optics-related business interests – they make their own high-end cameras and lenses, after all – this patent was specifically filed by Sony Interactive Entertainment, the division from the company responsible for PlayStation. Additionally, the patent specifically mentions the use of two Fresnel lenses in front of a screen for use in a “head-mounted display”.