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Why do lens in VR Headsets have a large focal length?

rhlkhna2463
Honored Guest

The focal distance of lens in Google Cardboard devices is around 5 cm but in other headsets like Oculus Rift and HTC Vive, it is above 1 m! Why is there such a huge difference? How does this affect the performance or the picture quality?

Why do we need a large focal length for the high end headsets?

1 REPLY 1

kojack
MVP
MVP
There's too different things here. The focal length of the lenses is the distance from the lens to the screen. That's around a few cm on all headsets (cardboard, rift, vive, etc). That's the 5cm you mentioned.
But the accommodation distance (where you focus your eyes) is much further on all headsets (including cardboard). The Rift DK1 was infinity. The DK2 and above are around 1.5m.

Our eyes get stressed when there's a conflict between where we want to focus (based on stereo vision) and the effective accommodation distance of the headset. So you want it to be at a comfortable distance that is also where a lot of things you are looking at will be. 1.5m tends to be a reasonable value.

I can't find details of the carboard's accommodation distance, but it's going to be somewhere from 1m to infinity.
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