Hmmm that’s interesting, didn’t know that existed. I wonder how that mechanism works.
I guess one way to do it would be to move just the lens, not the panel, but then you’d also need to move the distance between your lens and your eyes. They probably did something different … very interesting
It’s only on pancake lenses so far so, like I mentioned, I assume it is changing the distance between the 2 lenses on each eye, so the magnification is slightly adjusted. I don’t see how this would be possible with any other type of lesnes like aspheric (I guess you could stack them?). The suggestion of just swapping out lenses with your own perscription but it’s basically just perscription lenses but a bit more seamless.
Yeah but like I said above, I’d say if you’d increase distance between lens and panel, you’d also need to increase distance between your eyes and the the lenses. Not sure if they work like that though, maybe …
I was there and also had an/this issue, as I mentioned in my observations post. I discussed it with Seb during the meeting and while we both observed that something felt off, not entirely right, we couldn’t really put our finger on it: he was indeed astonished that he could see better w/o his glasses, while I (being farsighted) wouldn’t be able to see anything crisp unless I used my glasses (which unfortunately were the varifocal ones so I just got a tiny space with full clarity). We weren’t able to really figure out what exactly caused these observations.
And yes, I have the same odd feeling with the 8KX. The point is, about a year or 1,5 ago, when I exclusively used the 8KX for a couple of weeks, I wouldn’t feel the same amount of eye strain during use anymore, albeit perhaps still more fatigue than usual after being in VR remained. I attributed this to the ability of the brain to accommodate, as I experienced it to the extreme with my varifocal glasses: the first time I put them on, I was shocked - it was a hell of distortions, no straight line would appear to be straight, and I saw at least 3-4 distinctly different areas with each their own kind of weird set of distortions. A couple of days later I forced myself to wear them for a couple of hours, and did the same for about a week. At the end of that week I wasn’t able to see any distortions anymore, even if I tried to find them.
So you could say, eventually this issue disappears for the user, all is good. However, when I switched to the G2, and used the 8KX weeks later again, I noticed them more prominently again, and as said, the fatigue was never entirely gone, and the spacey feeling in VR was never at 100%.
So I guess this is accommodation thing is a major issue for the team working on such a headset development: their brains will adapt, they simply will lose the ability to see such issues.
Ha, I think it’s like this: what Vive did is indeed change diopter, you then only need to change the distance between the panel and the lens. That way it will get focus/vague depending on your setting. Now what Pimax would need to do is make a mechanism that would move at the same time the distance between the lens and panel AND the distance between your eyes and the lens. Then it would not change the sharpness, yet it would change the focus distance, so the projection would get further/closer to your eyes.
Yeah. The XTAL rep said that wide FoV headsets need short focal distance. I haven’t heard why but I speculate it might be because of pupil swim/distortion being a much bigger isue on wide FOV.
The focal distance on the Quest two is 1.3 meter https://twitter.com/id_aa_carmack/status/1371485209603022853?lang=en I really do wonder what the focal distance is on the XTAL and 8kX and also on the Crystal. I think they’re indeed all 3 really short and that’s what’s causing the issues we notice (eye strain and/or things not being sharp)
Hello everyone 
Thank you, a thousand times for coming to Paris, I talked about it the other time at #sweviver and it’s super nice to come to my city.
I just registered and from 5 p.m. I will be there to test the Crystal and the portal.
Thank you a thousand times, you have just given immense joy to old Ultrageek of vr since 2012 and the beginning of vr.
Thanks to the #Team Pimax for coming to Paris in the city of light
Aplushhss /Laurent/Lolof1 .
Actually, according to the livestream the guys did with Martin, the Crystal lenses are a form of ‘pancake lens’.
@Axacuatl I don’t think users should have to rely on adaptation. I’m sure you’re right, and we do adapt over time, but that’s not an optimal solution.
Nasa did an experiment that had people wear upside down view classes, and in a matter of a day or so, they saw everything correctly through the glasses. Then when they took them off, they had upside down vision again until they re-adapted. But I think making the lenses HMD frame adjustable somehow fore and aft for the focal length needed for each eye is a much better solution. I"d rather Pimax spent a bit of extra time on this and got it right rather than release it with the 8kx ‘change thickness’ solution as the only fix.
Cheers
Dave
@lolof1 I wish they could come to Canada… but even if they did, the travel time from province to province and city to city here is very long, so I probably couldn’t attend anyway! Post a video or a at least your impressions please!
Exciting times!
That is incorrect.
They are definitely run of the mill aspherical lenses.
I was there and also had an/this issue, as I mentioned in my observations post. I discussed it with Seb during the meeting and while we both observed that something felt off, not entirely right, we couldn’t really put our finger on it: he was indeed astonished that he could see better w/o his glasses, while I (being farsighted) wouldn’t be able to see anything crisp unless I used my glasses (which unfortunately were the varifocal ones so I just got a tiny space with full clarity). We weren’t able to really figure out what exactly caused these observations.
And yes, I have the same odd feeling with the 8KX. The point is, about a year or 1,5 ago, when I exclusively used the 8KX for a couple of weeks, I wouldn’t feel the same amount of eye strain during use anymore, albeit perhaps still more fatigue than usual after being in VR remained. I attributed this to the ability of the brain to accommodate, as I experienced it to the extreme with my varifocal glasses: the first time I put them on, I was shocked - it was a hell of distortions, no straight line would appear to be straight, and I saw at least 3-4 distinctly different areas with each their own kind of weird set of distortions. A couple of days later I forced myself to wear them for a couple of hours, and did the same for about a week. At the end of that week I wasn’t able to see any distortions anymore, even if I tried to find them.
So you could say, eventually this issue disappears for the user, all is good. However, when I switched to the G2, and used the 8KX weeks later again, I noticed them more prominently again, and as said, the fatigue was never entirely gone, and the spacey feeling in VR was never at 100%.
So I guess this is accommodation thing is a major issue for the team working on such a headset development: their brains will adapt, they simply will lose the ability to see such issues.
I don’t have nearsighted or farsighted. The problem I spoke of won’t go away…I believe it is a distortion. It’s not a matter of adapting…it is always there whenever the car is off of an angle sitting on a bank in a Daytona oval track. When I look at the displays on the left and right of me, I am getting crossed eyes and there is no way I want to focus on something that put strained on my eyes. And it’s not like the left and right is that far from the center…it’s only a 12 or 24 inches from the center…But when I look in the middle area, everything look normal OR when the car isn’t off an angle and on even level ground, everything is looking normal even the left and right. So, I think it is distortion at the edge of the lenses.
Custom 3D printed spacers for the face pad. I think the lenses are afixed to the hmd with magnets, so it should be possible to build a kind of Corkscrew based mounting solution within the pad for the lens so that you could set lens distance independently for each eye.
So… First of all: I know nothing about optics whatsoever, alas, but even somebody like each and every one of us here can intuit that if I have, say, a 180° FOV headset, and I can not reduce eye relief enough, when wearing it, so that there is actually a sliver of lens 90° out from my cornea, to look through, then we have a bit of a problem… :7
From what I have heard, the diopter adjustment in the recent headsets with pancake optics, which are all the rage at the moment, is done through moving the middle element in the three-lens/reflector stack.
(Also: I would presume the reported better stereo overlap in these headsets is down to greater magnification allowing for smaller screens, which means those screens will not bump up against one another in the middle, nearly as early.)
…but “all” we really need to do, for our single-lens devices, is to modulate the distance between lens and screen, just like when you focussed sunrays into a burn point using a magnifying glass, as a kid.
As I’ve mentioned a few times on this forum: The Oculus Rift DK1 came with three pairs of identical lenses, set into mounting tubes of three different heights, giving three fixed diopter options. Samsung’s ancient GearVR smartphone-drop-in HMD had a thumbwheel for dialling in the focus, so this is not exactly something new.
Even without an actual built-in mechanism, it should be perfectly possible to adjust lens-to-screen distance using shims under the swappable lenses, or e.g. screws around the perimeter, which act as “feet” for the lens, albeit only to increase the spacing – decreasing it, one would think, would require a more invasive procedure…
The only time you would need to have eye relief compensating in real time for diopter adjustments, would be if A) it is actually the lens that is moving/transforming, and not something else, and B) you are continually adjusting on the fly, to focus on whatever you are looking at, at any given moment, at the right focal distance, corresponding to the distance to the thing in the virtual world.
Oculus’ first “Half Dome” varifocal prototype used servos to move the screen back- and forwards. Later prototypes instead had the lenses suspended on thin leaf springs acting as parallel link arms, and they were actuated by speaker coils instead of motors, which was a much faster and quieter solution – apparently the variations in eye relief inherent to this was a relatively minor problem…
You would probably want the distortion profile to adapt to the modulating optical train, though – there is a bit of a “zooming” effect.
This also affects the eye tracking camera, which in the Reality series HMDs watches your eye through the lens.
It is possible the eye tracking calibration procedure could be enough to compensate for warping associated with changed diopters, as long as we stick with fixed focus optics. (EDIT2: …maybe even enough for entirely different lenses, such as the 42ppd option, or hypothetical third-party offerings, but that sounds less feasible.)
I am at a complete loss as to why wide FOV would necessitate a short focal distance - such a claim smells more than a little fishy to me…
So… No matter how well one may have engineered one’s lenses, using mathematical models; At some point the rubber must hit the road – that is to say, one need move on from the theoretical realm, and actually peer through the physical lens, produced in the real world, which one wrought by one’s calculations, and see what things really look like, and this is where subjectivity comes in.
…and this is where I could really see somebody with severe myopia experimenting, and determining: “Yep, this is it: At this distance between my beautiful lens and the screen, things look perfectly sharp to me – chisel down these numbers and built me a million units! -No, we don’t need a greater sample size, nor optical measurements using instruments.”
You might think this scenario preposterous, and that no engineer would be so cartoonishly lackadaisical, but I will remind you that this is the company that posted on this forum, several months after 8k/5k release, something to the effect of: “Hey guys. We’ve got some calibration equipment now.”
I’ve got my own little generic-lens-equipped “viewing box” (…or whatever one should call it), right here, which is entirely roughly “handheld-tuned” to where it “feels comfortable” to look into, for me, with my eyeballs. To anybody else, it would undoubtedly be terrible. But then - I am no engineer in any way, shape, or form, nor a businessman aiming to sell something to the masses. :7
About “cross-eye-ing” discomfort, I think we have discussed more than a few times on this forum, how the canting leads to the spot in each view that is best in focus, pointing 20° apart, so looking to the side brings one eye into focus, and the other out of focus. This wouldn’t be a problem if the whole view was in focus - then we wouldn’t notice, but it isn’t, and getting it all in focus is not an easy thing to achieve. (…although we do have some users who earnestly-seeming claim that is what they do see in the headsets…)
As for eye relief… Ye olde Rift DK1, again, had this through telescopic linkage between the HMD body, and the face gasket. So did the Vive, and so does the Valve Index.
…and I’ll reiterate my assessment, that for a wide FOV headset (…which I suppose leaves Crystal somewhat in the clear, in this case), one MUST have Z positioning.
EDIT: Heh, I wonder if one could get Jeroen of the Huygens Optics Youtube channel interested in VR, and have had the Pimax contingent drop by his place when they were in the Netherlands anyway, and leave behind a pile of lenses for him to evaluate… 
Ah, I don’t mean moving the distrance from the panel, just between the 2 lenses that make up one eye of the pancake lenses. I would imagine the lens on the panel side stays in the same place.
Your story reminded me of when I attended a convention and brought my 8kx, about 100 people tried it out and everyone loved it except for one guy who after taking the headset off actually had double vision for around 30 minutes. He was quite upset by this. Like his brain adapted to the headset and when he took it off everything went haywire.
This is indeed great for sure. You might recall iirc @LukeB used 1.5mm washers to remove the myopic to normal vision(on the p4k). As I recall he is farsighted. I think a kickstarter member did something similar with the 5k+? to improve eyestrain in there case.
With easy lens swap makes a variety of possibilities/upgrades. It could also depending on pimax’s position also allow 3rdparty to make a set of lenses with a distortion profile.
It would be great to have @Neoskynet(One of the KS M1 Testers) to goto one of the EU roadshows and give feedback as he had proposed pimax should redesign the KS lenses due to limitations he observed.
Well if you recalled alot of Cardboard VR shells would allow you to adjust Focus to screen per eye. Now very crude in that setup. I remember Luke had that on his wishlist for his next hmd and since pimax did not have it in the KS chose not to back.
Google cardboard were also designed with basic per eye focal adjustment.
Not my Zeiss Cardboard 
