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Why do we have fresnel lenses?

Roaster
Rising Star
The reviews I'm seeing say the lenses are VR's biggest failure.  Rift and Vive both.  I was told the lenses were highly optimized for the screens.
I can live with delays. I don't care about the cost. I can live with more weight. I don't care about the games list at launch. I do care about image quality and clarity, and would simply pick the unit with the best show.  How are these light glare artifacts acceptable?
Would reducing the brightness help?  Can the lenses be replaced with some custom solution?
i7-5820K @ 4.2Ghz, water cooled, Asus X99-Pro USB 3.1, 48 Gb DDR4 2400, Samsung 950 pro M.2 SSD, GTX 980 Ti SC, 750w psu
61 REPLIES 61

Tinindil
Expert Protege
Thanks W_Ben - had not looked into, but makes sense.

Anonymous
Not applicable


Fresnel lenses are designed to bend light, similar to a magnifier, except instead of a continuous curve designed to bend light to a single focal point, they have steps that are designed to bend light into a cylindrical shape. 

The effect is that you can take something that is wider than your field of view and condense it.
Each step in the lens bends a certain amount of light at a specific angle..., the more steps in the lens, the higher the resolution of the image seen through it.


Nope, wrong.

Both Fresnel lenses and normal lenses are designed to do the exact same thing, and that is either:
a. Shaping light from a single source point into parallel lightrays ( a lighthouse does this)
b. Taking parallel lightrays and bending them to a single focal point ( the lenses in the Rift/Vive, sniper scopes etc do this)

The reason Fresnel lenses are used is because they are thinner than full lenses and therefore weigh a lot less. The angles of the surfaces are still the same however so they bend the light in the same way as normal lenses.

Also, when using Fresnel lenses the light has to travel through a lot less material so the image is generally a lot clearer, but because of the many ridges glare is introduced as the light bleeds out of the edges of the steps.

Having more steps doesn't mean the resolution is automatically higher, since this is determined by the screens instead of the lenses. The use of more steps just ensures the lenses can be thinner and lighter, but in turn introduces more glare.

edit: To clarify, if the middle steps of the Fresnel lenses are angled slightly different from normal, the sweet spot becomes bigger, but will appear less focussed.

Roaster
Rising Star
Fresnel lenses have a place in 60" lighthouse lenses, or cheap glass lantern chimneys, or inexpensive stick on lenses for the back of a school bus, or a solar cooker, or an overhead projector ... but not in fine optics.  It just isn't done.  I just disagree with the choice that was made.  Perhaps someone from Oculus could shed some light on the why.  Since Vive and Rift both went the same way, there must be a good reason.
When I say I wanted the best, I meant the choice with no compromises regarding clarity. Weight and cost seem to be the deciding factors here.
i7-5820K @ 4.2Ghz, water cooled, Asus X99-Pro USB 3.1, 48 Gb DDR4 2400, Samsung 950 pro M.2 SSD, GTX 980 Ti SC, 750w psu

Hargert
Explorer
I have to agree and I would have liked to have an option for a regular lens. I am thinking it is because of the way that everyone harped and complained about the SDE. That feedback led to the choice to pick the lenses that minimized them the most and the god rays were considered less of an issue. I am sure as the tech develops and better LCD screens come along they will be replaced with normal lenses.

Kalec84
Heroic Explorer
i'm looking for a picture of this god rays problem, anyone can link a screen?

Roaster
Rising Star
http://doc-ok.org/?p=1414
http://www.pcgamer.com/oculus-rift-review/
i7-5820K @ 4.2Ghz, water cooled, Asus X99-Pro USB 3.1, 48 Gb DDR4 2400, Samsung 950 pro M.2 SSD, GTX 980 Ti SC, 750w psu

AntDX3162
Heroic Explorer

KingK76 said:



Roaster said:

My first flat screen was a 42" plasma at 1080 and I was blown away every time I turned it on.  I bought the DK1 and 2 because they were the best available at the time, and will do the same for the current gen units.  I just naturally want the best, and these fresnel lenses seem like a terrible compromise to achieve some goal ... something other than clarity. 
My question is, why fresnel lenses?


Did you pay $20000 for that Plasma?  If you didn't then you were not using a "FIRST GENERATION" Flat screen Plasma.  I would wager to guess that when you bought your first Plasma the model you purchased was a few generation in.  First Gen sucked, and they only lasted a year or so because the screen burn-in was SO bad.  Look it up.  And yes I wrote Twenty THOUSAND dollars.


They say it's 600Hz but it does not look 600Hz at all unless my brain and eyes are different.

Plus there is massive flicker like it's CRT and it eats massive power.  It heats up the room like a heater too.

If it anything it might look more natural for reproduction wise than anything at the time.  I'm not as sensitive to proper sRGB as I am to motion.  The Z35 says to have 100% sRGB and it's 200Hz.  Only problem is the black smear when in motion at any fps.  It's not noticeable unless looking for it.  Performance wise, the width and the smoothness psychologically increased my motor skill and neurological accuracy in real-life.

Because I use the computer so much my eye and head muscles work within a certain field of view.  When it got wide I found out I look further than I ever used to with 21:9.  I can look end-to-end with my eyes w/o getting head shakes as I used to with only 16:9.  There should be studies on this to be honest.

I'm sure with using the wider FOV of Oculus or any eq. HMD VR devices more than a primary monitor, more enhanced real-life performance would occur.
facebook.com/AntDX316

Roaster
Rising Star
My plasma was definitely not first gen.  I'm a blue collar air conditioning guy, and the price had to come down to the $900 range for me to buy in, around 98-99 I think. The picture is just stunning though.  Poor thing got killed in a thunderstorm though. Panasonic Viera.  Liberty Mutual gave me a full replacement cost award, so cool.

Speaking of cost though, I dropped $1500 on a camera lens, $600 for a telescope eyepiece, and would have no problem at all paying more for top of the line optics in a HMD.  J.H.C, it's a display.  That's the first priority.
i7-5820K @ 4.2Ghz, water cooled, Asus X99-Pro USB 3.1, 48 Gb DDR4 2400, Samsung 950 pro M.2 SSD, GTX 980 Ti SC, 750w psu

evilgrin
Explorer
can people mod the lenses? ive seen them taken apart

maxpare79
Trustee
OK those wondering about the god rays it's the best video I could find, someone did a short video thru the lens with a cellphone, keep in mind that the image looks sharper then this in RL, it's just a bit out of focus....

What you are looking for are a few lights circles starting at approximately 27 secs in when he looks down at the controls...it doesn't seem to be that bad but it is present...

https://www.youtube.com/watch?v=SXJav7NEl4w
I am a spacesim/flightsim/racesim enthusiast first 🙂 I9 9900k@5.0, 32gb RAM/ 2080ti Former DK2, Gear VR,CV1 and Rift S owner