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Purpose of Fresnel Lenses

zbosonzboson Posts: 994 Poster of the Week
edited November 2016 in General
I would like to know the reason Fresnel Lenses were used in the CV1.

The only reasons I am aware of are to reduce chromatic aberration away from the center of the lens and to improve focus away form the center.  Are these the main reasons? Are there other reasons?

It seems to me there should be other reasons because after using the DK2 now for the last month or so at home and the CV1 at work I can say that I would rather have chromatic aberration and the worse focus away from the center of the lenses than putting up with god rays in games such as ED. God rays also make it a challenge for text which tends to have strong contrast (e.g. black on white). Without Fresnel lenses you can always look in the center of the lens which would have no god rays, no chromatic aberration, and good focus but with Fresnel lenses you can't avoid the god rays by looking in the center of the lens.

Comments

  • SakkuraSakkura Posts: 267
    Nexus 6
    edited November 2016
    Fresnel lenses are a lot smaller and lighter than conventional lenses.
  • zbosonzboson Posts: 994 Poster of the Week
    Sakkura said:
    Fresnel lenses are a lot smaller and lighter than conventional lenses.
    That's an interesting point but is that really a significant factor in the weight of the CV1?  The PSVR HMD is heary than the CV1 but from what I hear more comfortable.
  • FrozenPeaFrozenPea Posts: 2,535 Valuable Player
    edited November 2016
    Well it is mainly due to the the reasons you mention. 

    I think the problem is ED was not designed for the CV1 len's so the flaws are more obvious. I don't play ED and I rarely notice god rays because I'm playing games like Chronos, Damaged Core, Dragon Front, Eagle Flight etc that were all designed for VR from the ground up and design choices were made to reduce God Rays.

    In Dragon Front for example there is a lot of text but I've never really noticed God Rays because they've designed well to avoid/minimise God Rays.

  • Sax-a-boomSax-a-boom Posts: 731
    3Jane
    FrozenPea said:
    Well it is mainly due to the the reasons you mention. 

    I think the problem is ED was not designed for the CV1 len's so the flaws are more obvious. I don't play ED and I rarely notice god rays because I'm playing games like Chronos, Damaged Core, Dragon Front, Eagle Flight etc that were all designed for VR from the ground up and design choices were made to reduce God Rays.

    In Dragon Front for example there is a lot of text but I've never really noticed God Rays because they've designed well to avoid/minimise God Rays.

    Yeah what he said. A well designed game that has been built from the ground up for VR, avoids the high contrast flares and difficulties with text. Know your medium. I think we're on an upward curve.
  • zbosonzboson Posts: 994 Poster of the Week
    edited November 2016
    I agree that developers can avoid god rays. I made the anoalogy with NTSC (aka never the same color) where you avoided strong reds because they bled. But these kind of adjustments come at a price (e.g. no strong reds with NTSC).

    Some games won't work with these adjustments and I think that includes ED.
    https://forums.oculus.com/community/discussion/comment/452435/#Comment_452435

    So that means there are some classes of games which can't be done right due to god rays.  And I think not just games. Applications which need text I think are going to be difficult due to god rays. We will see when the Oculus browser Carmel comes out. I'm a bit skeptical.
  • FrozenPeaFrozenPea Posts: 2,535 Valuable Player
    edited November 2016
    yeah so in that very specific scenario god rays are obvious and makes the god days problem feel worse than dk2 lens. (I'm just going by what you're saying as I haven't tried ED.)

    However I would argue that loosing quality in a small fraction of games to god rays(that can also be minimised by software/design) is better than loosing quality in all games to chromatic aberration and worse sweet spot. 

    In the end it was all about compromise and trade off's so someone was going to loose unfortunately. Hopefully one day someone will invent a far superior lens that has none of these problems and I'm sure Oculus will be the first to jump on it.
  • Atmos73Atmos73 Posts: 3,128 Valuable Player
    I'm 100% convinced HMD's with any sort of lens will quickly die off.

    HMD's where the image is projected direct on the retina is the future. I say future but the tech is already in use.



    Fresnel len's are horrible.

    DK2 owner - Vive owner - Pimax 8k backer - Waiting for Knuckles on Valve time.
  • FrozenPeaFrozenPea Posts: 2,535 Valuable Player
    @Atmos73 I agree, I was thinking about what Magic Leap are apparently using as well which is meant to be the 'next step' but who knows when we will see anything real from them! :)

    "All three major MR headsets rely on images that are projected edgeways onto a semitransparent material—usually glass with a coating of nanoscale ridges. The user sees the outside world through the glass, while the virtual elements are projected from a light source at the edge of the glass and then reflected into the user’s eyes by the beam-splitting nano-ridges. Magic Leap claims that its device is unique in the way it beams light into the eye, though the company declines to explain it further at this time."

    Link: https://www.wired.com/2016/04/magic-leap-vr/
  • ChoronzonChoronzon Posts: 341
    Nexus 6
    As someone who persists with DK2 I don't find CA troublesome - in fact, it's hardly noticeable. Devs may learn to minimise lens-flare, but for video it's here to stay. I cannot believe Oculus will continue with Fresnel lenses unless it can be fixed.
  • zbosonzboson Posts: 994 Poster of the Week
    I also don't find CA that troublesome with the DK2. Maybe I should try ED with the DK2 again. Perhaps it's better even if the resolution is worse.
  • ZoomieZoomie Posts: 1,777 Valuable Player

    You're going to find text very blurry if you go back to Elite with a DK2 from a CV1.
    There is a way to turn your interface green which helps due to the pentile layout.  I found it helped mitigate the lower resolution, somewhat.

    Any sufficiently advanced technology is indistinguishable from magic.
    - Arthur C Clarke
  • SakkuraSakkura Posts: 267
    Nexus 6
    As someone who persists with DK2 I don't find CA troublesome - in fact, it's hardly noticeable. Devs may learn to minimise lens-flare, but for video it's here to stay. I cannot believe Oculus will continue with Fresnel lenses unless it can be fixed.
    It can at least be reduced. It's just the particular tradeoff they made with the CV1.
  • MradrMradr Posts: 3,523 Valuable Player
    edited November 2016
    The trade off is to do what Vive did, but at the same time - there are other lens technology coming out soon that might work a little better from control to the weight it self, but stuff like this is always around the ben in the river - the question is do you wait or just do what you can with what you have?

    https://www.newscientist.com/article/2091826-metamaterial-lens-is-thinner-than-the-light-it-bends-and-focuses/
  • ZoomieZoomie Posts: 1,777 Valuable Player

    This is the problem.  People talk about Vive and Oculus choosing to use Fresnel as if there was a cheaper, lighter, sharper lens with no drawbacks.  It's not like both of these companies had a better option and stubbornly chose to use an inferior one out of spite. 

    Fresnel lenses have advantages and disadvantages.  To both of these cutting-edge companies, the juice was worth the squeeze.
    Fresnel lenses give you a large sweet-spot, sharp focus, and reduce chromatic aberration.  They're also light, and give a fairly consistent focal depth from middle to edge. 
    Unfortunately Fresnel lenses suffer blooming when non-incident light hits the ridges, resulting in what everyone calls "god rays". 

    This is a problem with optics, not with poor design choices.  I'm interested to see PSVR because they used more traditional lenses (IIRC) and according to many people that's the route Vive and Oculus should go.  I have a feeling people are simply not recognizing all the drawbacks those traditional lenses bring to PSVR. 

    The solution isn't just to spend more money and suddenly get perfect optics.  High end glass costs a lot, but it also adds weight.  If people honestly see PSVR's image as the best compromise, maybe Oculus and HTC will choose that route for the next gen devices.  In terms of lens performance Fresnel offers a lot of advantages, but it does appear that some people can't look past god rays (pardon the pun).

    Any sufficiently advanced technology is indistinguishable from magic.
    - Arthur C Clarke
  • Sax-a-boomSax-a-boom Posts: 731
    3Jane
    From a personal point of view the rays don't really bother me. It's also interesting that lens flare and ghosting is often added to games and movies to add a sense of realism.
  • zbosonzboson Posts: 994 Poster of the Week
    Another important factor is cost. How much more do the Fresnel lenses cost (if they cost more)? Are Fresnel lenses one reason the CV1 is so much more expensive than the DK2?
  • MradrMradr Posts: 3,523 Valuable Player
    edited November 2016
    zboson said:
    Another important factor is cost. How much more do the Fresnel lenses cost (if they cost more)? Are Fresnel lenses one reason the CV1 is so much more expensive than the DK2?
    Well there are a few reasons behind why the CV1 cost different than the DK2.
    1) Dual screens (125 a screen) = 250$
    2) DK2 wasn't design with a refine design (you can find customer grade elections inside it)
    3) DK2 didn't have mark up either.. but was also design for in house limited support compare to CV1
    4) etc

    The lenses themselves might have added cost, but it would've been around 60-90$ a pop once you remove the worker cost, the mark up, the headset design/elections, the cost of working on the design etc etc. Lenses themselves don't cost much to make once you go mas market (yes your glasses are overprice as most glasses are design and solid by one company that controls most the market - by as high as 80%).
  • zbosonzboson Posts: 994 Poster of the Week
    I wonder if Oculus could have used a single screen with much higher resolution to compensate for the wasted pixels. I mean is it cheaper to use a single screen with higher resolution or dual screens with lower resolution. I would guess that due to the economics of scale that a single cell phone screen could be cheaper but maybe Oculus uses mass produced dual screens anyway.
  • LZoltowskiLZoltowski Posts: 6,774 Volunteer Moderator
    edited November 2016
    Atmos73 said:
    I'm 100% convinced HMD's with any sort of lens will quickly die off.

    HMD's where the image is projected direct on the retina is the future. I say future but the tech is already in use.



    Fresnel len's are horrible.

    I have a pair of those. BUT there is a drawback to this tech at the moment, if you dont look directly into the centre of the image looses quality. It is a beautiful display when it looks 100%, you cant see any pixels, the clarity and colours are like looking at an 4k OLED screen BUT it is not full view ... its like looking at a medium sized cinema screen.

    The biggest issue with this tech is field of view. If you are not in the sweet-spot it degrades considerably.
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  • Atmos73Atmos73 Posts: 3,128 Valuable Player
    edited November 2016
    That tech isn't VR ready yet I agree. But sooner or later they'll hit that 4k sweet spot I just hope it's less than 3 years away.
    DK2 owner - Vive owner - Pimax 8k backer - Waiting for Knuckles on Valve time.
  • voidxnovoidxno Posts: 37
    Brain Burst

    I would love for CV1(+1) to have removable lenses as DK2. Make a good seal and users responsibility for dust if opened. We could have 1st/3rd-party lenses with different properties: fresnel/not, weight less/more, focus spot size, god rays/not, built-in prescription, and more. New marked with personalized preferences.

    Yes, would probably need a lens distortion plug-in interface. But make it a feature, not a limitation.

  • Atmos73Atmos73 Posts: 3,128 Valuable Player
    I was a bit skeptical about projecting direct onto the retina but then you realize how many problems lens based imaging bring and can't be eradicated even with more expensive lens's. I mean to increase field of view fresnel lens would mean an even bigger HMD.
    DK2 owner - Vive owner - Pimax 8k backer - Waiting for Knuckles on Valve time.
  • DerekSpeareDerekSpeare Posts: 204
    Nexus 6
    edited November 2016
    I have both the DK2 and CV1.  The DK2 looks better in the sense of being more "crisp"...hard to explain, the SDE notwithstanding.  The lenses on the CV1 could be much better.  The godrays are quite unappealing.
    derekspearedesigns.com
  • edmgedmg Posts: 1,149
    Wintermute
    Can't speak for the DK2, but some of the big reasons I rarely use my Vive any more are the chromatic aberration and blurry text towards the edges of the screen. I'll trade the Rift's worse god-rays for better colors and less blurring than the Vive any day.
  • Arock387Arock387 Posts: 729
    Trinity
    Having worn glasses basically my entire life I'm used to these rays and glares of light.  Its basically the same in the Oculus Rift.  So it doesn't bother me at all
  • chaven.yenketswamychaven.yenketswamy Posts: 3
    NerveGear
    Fresnel lenses cause less eye strain and also reduce Chromatic aberration which is an issue with lenses like in the GearVR. Hopefully this will change with the recent breakthrough in optics where we can now make lenses without CA and still be cost effective. 
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