Is it possible to fully eliminate camera disparity in VR?

my colleague and I work on perception in VR, so we need to eliminate the stereopsis effect in VR. Therefore, we tried to set the cameras of the left and right eye at the exact same position. Even though they are at the exact same position the pictures projected to the HMD do have a small but noticeable disparity.
We also compared screenshots at different camera locations and came to the conclusion that there is a difference between the pictures we see in VR (HMD) and on the Unity screen. We have the same issue independent from the hardware, both Oculus Rift and HTC Vive.

Does anybody know where this disparity is calculated, when it is applied or how to prevent it?

We could really use any help!

Thanks a lot!

 

You would likely have to skip all of the VR plugins and settings and make your own down-the-center view and run it on Cardboard as just a regular app.

I think all of the VR plugins (SteamVR, OPenVR, Oculus, Cardboard) all try to do the split and distortion automagically, WAY before you get to play with it.

Personally I can't imagine trying to do the lens distortion myself but I've seen a few math folks who say it's actually some straightforward equations.