There’s been some debate recently as to the cause of the IPD measurement discrepancy issue on this forum. @risa2000 has been nice enough to provide an explanation as to those discrepancies in these two threads: here (Some thoughts on the IPD discrepancy ) and here (Clarifying Near IPD x Distant IPD confusion .
In my view Risa’s explanation does not adequately serve to explain the cause of the IPD measurement discrepancy. It serves as a useful tool to understand how cantered lenses work that’s for sure. It doesn’t explain why theres a 10mm less software ipd reading when by geometry and divergence it should result in additional measurement added to software ipd reading to compensate for the reduction in the space between the centre of the lenses which a divergent display would cause over a 180 degree flat planed VR lens.
Risas own diagrams illustrate this if you look at the fact the flat planed diagram he shows has a greater IPD range than the divergent diagram IPD that he shows.
Risa’s explanation relies on the centre of the lenses not being the focal points. My explanation conversely relies on the centre of the lenses being the focal points for the eyes.
For deliberation between both points of view you have to ask:
Why even have the smallest circle fresnel rings indicating the centre of the lenses if that’s not actually where the sweet spots are ??
Much more likely everyones looking at the inner edges of the sweet spots which fall within 65mm IPD since 70mm is the true minimum, and the diameter of the sweet spot is 2.5mm-5mm in each direction from the middle of the smallest fresnel rings.
There’s no assumptions being made, the data speaks for itself. Theres a discrepancy of 10mm extra measurement between the physical lens distances and the on screen IPD setting, on screen IPD being 10mm less than physical distance.
Mathematics and geometry are saying it should be a smaller lens distance created due to divergence of panels and lenses, compared to a 180 degree plane and that should be accounted for with extra measurement on the software IPD reading to give an accurate reading, not a reduced software IPD reading.
The middle point of a line on a 45 degree angle is shorter than the middle point of a line on a 180 degree angle, which is why extra software IPD measurement should be added to compensate for the divergent displays to give an accurate 180 flat planed vr IPD reading (which corresponds to real IPD), not by reducing the on-screen IPD reading. This is my explanation for the IPD measurement discrepancy being 10mm less on screen than the 70mm physical minimum distance between the lenses on Pimax.
I believe the measurement discrepancy is caused by Pimax opting to reduce IPD to increase lens real estate as much as possible, and why the minimum distance between the centre of each lenses is 70mm, whereas most other 100 fov consumer vr headsets have a 60mm minimum IPD and IPD values which correspond to the users IPD measurements.
If anyone’s willing to chime in to explain how do Risa’s posts account for a lesser on screen IPD reading when it should in fact have a greater on screen IPD reading to compensate for actual IPD measurements since divergent displays result in a lesser IPD than a 180 degree flat-planed vr lens, seeing as they’re the only two explanations that make sense.
Does Pimax want to chip in and offer a solution for customers and backers that purchased the product with one of the main assumptions informing their purchase was that reviewers and product information said 55mm or 60mm IPD was the minimum required to use the headsets?
Some can’t use at 65mm, what about them? Even after extensive fitting adjustments.
As far as I see it everyone under 70mm IPD - 55mm IPD require a solution and address by pimax and until a solution is provided customers in those IPD ranges should be entitled to a refund who can’t use the headsst for even short periods or at all due to intense eye strain and discomfort.
I propose that the IPD issues of discrepancy and being unable to get a clear image in both eyes, and eyestrain issues could be solved by shaving off 5mm off the inner parts of each lenses towards the nose and creating a rubber adapter for the smaller 160/190 fov lenses, which sits at the outer peripheral part of the lenses, which will allow for compression of the adapter when IPD is adjusted outwards to the maximum value and an accurate on screen reading in comparison to real IPD measurements.
@Sean.Huang @anon74848233 @mozi @PimaxUSA An official response would be appreciated as to whether or not my abovementioned suggestion for a smaller lens design will be considered and implemented as a purchasing option and a replacement lens on store, as a smaller lens of -5mm off the inner side towards the nose and an outer periphary rubber compressible adapter would entirely solve the three problems.
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- IPD measurement discrepancy issues
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- Eye strain related issues.
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- Customers within the 55-65mm IPD ranges would be able to get clarity in both eyes at the same time.
Do you want replacement fresnel lens options sold on store with both 200 and 190 diagonal fov lenses offered? Or headset models with the option to choose which sized lens insert you want?
- Yes
- No
0 voters
I’ve brought both of these diagrams to approximate scale so my explanation behind the discrepancy can be easier illustrated.
Risa’s suggested focal points, which I suspect to be towards the outer edges of the sweet spots of both lenses.
