Measuring eye relief

[M]

Hello,

I am using HTC Vive Pro Eye in Unity which has integrated Tobii eye trackers. In my research I need to measure the exact value of lens/display distance to user’s eyes. In the headsets specifications, it only mentions it has adjustable eye relief. But it nevers mentions a value for it.
– What are the ways that I can measure this value (assuming I keep it at a fixed distance for all participants)?
– Does Tobii eye tracker provide eye images while the user is wearing and using the HMD in a Unity projects? Can those images be used for estimating the eye relief value?

Thank you for any help 🙂

[Grant [Tobii]]

Hi @maryam, thanks for your query. Whilst we do provide distance from the user’s eyes (gaze origin) to the origin of the eye tracker, which is situated in the lenses of the HMD. We unfortunately do not however provide a distance to the display itself.

With regard to eye images, Neither Tobii nor HTC provides this data for the Vive Pro Eye I am afraid. My apologies for the disappointing news, hopefully you manage to find a workaround for your needs.

Please do let us know if we can provide any further information. Best Wishes.

[M]

Hello Grant,
Thank you very much for your response.
“Whilst we do provide distance from the user’s eyes (gaze origin) to the origin of the eye tracker, which is situated in the lenses of the HMD.”…
So can you please guide me on how to calculate the distance of user’s eyes to eye tracker?
And I guess the eye tracker is almost in the same distance to the eyes as the lesnses are? Do you know how much difference there is between them?

Thanks again,

[Grant [Tobii]]

Hi @maryam, If you have some skill in programming then you can access this metric using the Tobii XR SDK where we refer to the user-eye tracking distance as the gaze origin, which originates from the eye. The 3D position of the eye relative the eye tracker can then be accessed by

TobiiXR.GetEyeTrackingData(TobiiXR_TrackingSpace.Local).GazeRay.Origin

We describe this in more detail @ https://vr.tobii.com/sdk/develop/unity/documentation/api-reference/

Hopefully, this should point you in the right direction, please let us know how you get on. Best Wishes.

[M]

Thank you so much. Yes, I am familiar with programming and that solution sounds good.
Just a last question, Do you know if the gazeOrigin variable in the TobiiXR SDk is the same value provided by the ViveSR SDK? (they also have a gazeOrigin metric, and I guess its the same things that Tobii provides?)

Thank you.

[Grant [Tobii]]

Hi @maryam, yes indeed I can confirm this is the same variable although it may be the case that they are measure in different units, so be on the lookout for that.

[Author]

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