Fresnel lens stack for "supernatural" FoV

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langmyersknow
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Re: Fresnel lens stack for "supernatural" FoV

Post by langmyersknow »

Wow this is really amazing and exciting. Maybe when we finally get our de kits we can mod it for even more fov.
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

langmyersknow wrote:Wow this is really amazing and exciting. Maybe when we finally get our dev kits we can mod it for even more fov.
As you can see from an earlier discussion with Palmer, the Rift Dev Kits have removable lens cups (eyecups), and the lenses are held in them with removable clips, so we CAN replace the lenses in an "unused" set of lens cups with anamorphic lenses.

Palmer said he previously used anamorphic lenses to expand 4:3 (1.33 AR) content to 16:9 (1.78 AR). I plan to go farther, expanding 8:9 (half screen width, 0.89 AR) to (almost) as wide as the eye can see. The Rift Dev Kit may be limited somewhat by the size of the lens cups and the frame around the lenses, but it should still be a significant increase in horizontal FoV (at the expense of pixel density, especially near the edges).

I will also do more with my other experiment involving a curved stack of 5 uncut fresnell magnifiers for each eye, wrapped completely around and touching the face from ear to ear. That version gives MAXIMUM FoV, with pixels everywhere you CAN look (but at correspondingly lower pixel density).

I love "as simple as possible", and this first version with trimmed lens stacks is developing nicely in that direction. Although I am designing it around my Nexus 7, even a dedicated 7-inch LCD panel may be used in its place (for a full DIY HMD).

Beware that we will need custom pre-warp plug-ins for these HMDs with different horizontal FoV, so it would be GREAT if HMD driver software allowed such plug-ins, or at least accepted a custom displacement map image or custom warp formula configuration.

For applications that can tolerate the reduction in pixel density (from spreading available pixels over a larger area), this significant increase in FoV is awesome and even MORE immersive.

But even without this increased FoV, the Rift ALREADY crosses the required threshold, and will be truly amazing even in its own default configuration. And for some applications, the increased pixel density from a smaller FoV may actually be beneficial. So different sets of lenses may be useful for different applications, even with the Rift Dev Kit.
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

Okay, I added the center portions of my fresnel magnifiers, for increase symmetric magnification. This got rid of the black borders at the edges. It uses the pixels very efficiently with almost no waste.

That third "uniform magnification" layer just sits inside on top of the other layers, partially held in place by the vent holes mentioned previously. They are easy to replace, so that different magnifications could be used for different people.

I will take some photos now.

EDIT: Here are the photos. It works quite well, especially for only $3USD in parts. :D

Note that all lenses except the 3x magnifier centers must have the ridges toward the eyes. The 3x center-cut lenses can be flipped either way.
Front:
gog-front1.jpg
gog-front2.jpg
Bottom:
gog-bottom.jpg
Top right:
gog-upright.jpg
Back:
gog-back1.jpg
Closeup of air vents:
gog-vents.jpg
Extra 3x magnification lenses (not installed):
gog-lens3.jpg
Extra 3x magnification lenses (installed, easy to remove):
gog-lens3a.jpg
Note that the 3x magnification lense cut from the fresnel magnifier centers can have the ridges toward or away from the eyes. In fact, the ones in the photos are cut identical, so one is flipped over (ridges away), and it works equally well. Perhaps it would protect them more to keep the smooth side toward the eye, so eyelashes brushing them would be easier to clean.

Also, when on the face, the portion that touches the skin spreads out more than when relaxed as in these photos. That has the effect of moving the lens stacks so that they are parallel to the display surface, exactly as needed.

This arrangement makes almost ALL of the pixels viewable, when the screen distance is adjusted to focus for my near-sighted eyes. Different eye prescriptions may require using a different magnification for the third layer, allowing the screen distance to be adjusted for full FoV while remaining in focus. In some cases (much more near-sighted) the third layer of magnifying lenses might not be required.

My 7-inch tablet display sits about one inch in front of the goggles. It will be held in place by an adjustable foamboard shroud, which I will construct later. All non-tablet parts are from a "Dollar Tree" store, with about $4 total parts cost (plus sales tax). It may need additional head support (such as a stronger strap) to hold the display weight in front of my face.

The left and right offset lenses were taped at top and bottom edges into a secure two-lens stack. The air vents actually held them inside the safety goggles. Although this actually held together and worked without tape, I added some tape at the top and bottom of the lens stacks, wrapped over the goggle edges, to secure them to the goggles.[/color]

The FoV Viewed through the fresnel lens stacks is MUCH larger than wearing the safety goggles without magnifying lenses. It extends beyond my nose, and my eyebrows and my mustache below (i.e. "supernatural" FoV).

I have impressed myself with this one (so far)! Soon it will need software support. I need to see how well the FoV2Go demo for Android devices works on it now. But it would look better with pre-warp and anamorphic adjustments.
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Re: Fresnel lens stack for "supernatural" FoV

Post by Fredz »

geekmaster wrote:The one image that is wide-eye view and appears to not have full overlap is this one
I was talking about the first one, under SDK | Calibration application. It's been created by Oculus, so I guess you won't find anything better than that in term of correct rendering for the 7" devkit.
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

Fredz wrote:
geekmaster wrote:The one image that is wide-eye view and appears to not have full overlap is this one
I was talking about the first one, under SDK | Calibration application. It's been created by Oculus, so I guess you won't find anything better than that in term of correct rendering for the 7" devkit.
Okay, thanks. I will try that.

Notice that I added photos of my "$3 HMD for 7-inch tablets" to my previous post. I plan to make an adjustable shroud from foam board (also from the dollar store) to block external light and to hold the display in focus. This may add an additional dollar to my materials cost.
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

I just tried the "Fov2Go Minus Lab" demo on my Nexus 7. Although I can merge the images easily with my naked eyes (no eyeglasses), the images are just too far apart to merge while wearing my fresnel stack goggles. I can see aspheric warping near the edges, but the central area all likes quite good, and the entire display is in relatively sharp focus for both eyes. Of course, I do not have a REAL Rift Dev Kit to compare against yet, but I did try this demo with the DIY Rift 5x aspheric acrylic loupe lenses, and that worked fine (provided I moved the lenses to a position that allowed me to merge the stereoscopic image pairs).

With this anamorphic stretching, I really need to move my image centers closer together. I have not tried the recommended 7-inch Dev Kit test image yet. I will try that soon (after my Nexus 7 battery recharges).

I am having fun with this. I like inexpensive and simple stuff. And thanks Palmer, for the Fov2Go stuff (and the Rift Dev Kits)!
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

Fredz wrote:
geekmaster wrote:REQUEST: Where can I get some stereoscopic image pairs that are already adjusted to work on the 7-inch Rift Dev Kit?
I'm tracking every shot I can find for the Rift here : http://vr.wikinet.org/wiki/3D_images

There is a least the one from the Oculus Kickstarter update that is adapted for the devkit, don't know for the others. I should probably categorize these images by device, but that will take time.
Fredz wrote:
geekmaster wrote:The one image that is wide-eye view and appears to not have full overlap is this one
I was talking about the first one, under SDK | Calibration application. It's been created by Oculus, so I guess you won't find anything better than that in term of correct rendering for the 7" devkit.
Okay, I tested these fresnel stack goggles with image that you recommended:

Factory Room Test Target:
Image

It looks pretty good, but also, it DOES demonstrate stereoscopic misalignment problems that Palmer Luckey warned me about. The effect is that for a round object near the center in one eye, but stereoscopically offset (by parallax) toward a side in the other eye, the non-linear anamorphic effect from offset lenses stretches the circle into an ellipse that gets wider toward the edge of the FoV. This makes it difficult to merge. And worse, things in the corners may get expanded higher or lower in one image IF THE PRE_WARP DOES NOT MATCH THE LENSES.

These problems can be fixed in two different ways. One is to use prismatic anamorphic stretching with a pair of back-to-back prisms (as shown in a previous link in this thread). Another method is to adapt the pre-warp algorithm to compensate for ANAMORPHIC warping. This includes making sure things in the corners keep the same height in both stereoscopic images, regardless of which one is closer to an edge. This anamorphic pre-warp can also assure that a circle remains circular and not elliptical as it approaches an edge of the FoV.

The central areas look pretty good, except the text labels above and below, which get their edges pulled outward asymmetrically from each other, disturbing stereoscopic merging. This can CERTAINLY be compensated for in software, but it PROVES that anamorphic lenses need DIFFERENT pre-warp than simple aspheric lenses. At least the central area works reasonably well with the WRONG pre-warp.

Now, the next step (after adding a shroud to mount the tablet display to the safety goggles) is to develop an anamorphic prewarp function (and/or displacement map)...

This DOES prove that software needs to support multiple different pre-warp filters, depending on choice of HMD optics.

EDIT: More testing with this factory test image, both with the extra 3x magnification fresnels inserted and with them removed, shows that there is too much magnification for me at the best focal distance, wasting too many pixels. When I test without extra magnification, I can see a small but noticeable amount of border around the edges. Perhaps I need an extra 1.5x magnification to fully use the available pixels on the screen. And the amount of extra magnification depends on the needs of the user, much like the eyecups on the Oculus Rift. For now, it looks sharper without the extra 3x fresnel. That could be because of less fresnel distortion, or it could be because of the higher pixel density with less magnification, but I suspect some of both...

This anamorphic HMD needs variable magnification for different people (just like the Rift Dev Kits), but also needs DIFFERENT pre-warp than the Rift uses, to keep things near the edge vertically aligned with each other in both eyes.
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

I tried wearing reading glasses, with the "2-lens-stack" googles over them. I put a bit of pressure on my nose with the fresnel lenses pushing against the eyeglasses. But the horizontal FoV was perfect at proper focal depth. The problem is that the eyeglasses do not cause aspheric distortion, so the top and bottome centers of the image collapse inward somewhat, letting me see past the screen edges up to the tablet edges. So for magnification, we really do need aspheric loupe lenses (or the fresnel equivalent). Just not a full 3X in my case.

Okay, next experiment. I put on my corrective eyeglasses so I have nearly normal vision. I wore the 3-lens stacks in the goggles (with extra 3x magnifiers), OVER my normal glasses. It was the best yet, with FoV vertical and horizontal. The problem is that I needed my small corrective lens that sit below my eyebrows very close to my eyes. Contact lenses would be even better. So assuming you have perfect (or corrected) vision, the extra 3x magnification layer is about right, I think. Everything in that test image looked pretty good except the text labels that had vertical misalignment preventing stereoscopic mergering of the text (until the pre-warp gets adjusted to compensate for that).

The problem with corrective eyewear is that it can push the fresnel stacks too far from the eyes, making this method not work well.

What would be ideal is to wear custom contact lenses that give you perfect vision AND focus about one inch from your face. Then you can just hold your tablet screen touching your nose and eyebrows. I tried it and I am sure it would work, giving maximum possible FoV. There are a lot of things to try, but many of them will require a custom pre-warp algorithm, and NOT the one that the Rift uses, That means we need custom pre-warp support in our drivers and/or games.

Soon, when I get my real Rift, this stuff may become a distant memory. But for those who have a tablet computer and will not soon get their Rift, they may want to continue my experiments here.

At this time, besides a shroud to attach my goggles and screen together and block stray light, I just need some custom pre-warp code, and then we can draw up some DIY construction plans.
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

My 5x and 6x magnification reading glasses arrived today. The "large" lenses are smaller than huge ones I got at the dollar store.

I tried wearing the 6x glasses while viewing the Fov2Go "Minus Lab" demo on my 7-inch android tablet (Nexus 7), but I could not merge the images. Their centers are too far apart. I was able to merge them while hand-holding a pair of 5x loupes (recommend for DIY Rift-clones) but only while holding the lens centers offset from my IPD so I was peering through the inner half of the lenses. When offsetting the lens centers like this, the image is shifted away from the lens center by an amount proportional to the distance from the lens centers.

When viewing through the eyeglasses, there was no distortion. Rectangles looked like rectangles. Vertical and horizontal edges were not warped. This is because eyeglasses are design with meniscus lenses that curve outward from the eye, which focuses your eye on a flat plane (such as a LCD panel held at a close distance).

The 6x lenses were not enough for the screen to fill my FoV, but they do focus nicely not very far from my face. I am near sighted, so with perfect vision they would probably focus even farther away. Based on this experiment, I suspect that I would need about 10x magnification to have the 7-inch screen fill my vertical FoV while it is in landscape mode.

Although the IPD distance for the Fov2Go demo was too large, the Oculus factory configuration demo looked great with these glasses, with good stereo merge (even on the text labels). The only problem was that the image had pre-warp distortion that these high-magnification eyeglasses do not need.

After a little more thought about my recent experiments with 3-lens fresnel stacks mounted in safety googles, I decided that the physical position of the lenses in the stacks, and relative to my IPD, is probably important. I just hacked them together by ROUGHLY cutting 6-inch magnifiers into 3 pieces and stacking those pieces. Although that works, and a pre-warp could be figured out (empirically through trial and error), it would probably change somewhat for each pair of VR goggles made that way. We need to assemble them with more precision, so that one pre-warp filter will work for all of them lens stacks, and for both eyes.

Thinking a bit more about fresnel stack pre-warp distortion, it is clear that using a stack of lenses with 3 DIFFERENT centers would require warping around all three of those lens centers. Each warp is like a portion of a single lens, and all three warps can be performed (approximately) in any order. Testing shows that it does not matter (noticeably) what order the lenses are in the stack.

Now would be a good time to document what I have been thinking, about how the lens stacks work. The fresnel lenses operate just like an equivalent solid aspheric lenses. To make the fresnel design simpler, they are usually modeled after solid lenses that are flat (planar) on one side and convex (curved outward) on the other side (i.e. plano-convex lenses). Here is a the wikipedia page, and a diagram showing two equivalent lenses:
http://en.wikipedia.org/wiki/Fresnel_lens
Image

A short and simple description of how magnifying lenses operate is that they make make an image appear larger when viewed through the lenses. The 5x lenses used in DIY Rifts enlarge 5x. To do that, they do not move the perceived position of a pixel viewed through their axis, but as you look further away from the lens axis (toward the edges), the perceived position of the pixels is moved away from the lens axis, by the original distance from the lens center multiplied by the lens magnification. A pixel 2cm from lens center would appear at 10cm from lens center, outward in the same direction.

Now, when moving the lens center so you are looking though a position closer to its edge, everything you see is pushed outward from the REAL lens center, that may be well out of your FoV. The lens stacks I use have a pair of lense that start at 1-inch outside of lens center, and extend to 3-inches outside of lens center. This means that EVERYTHING is shifted, and more so at the outer extreme. These outer portions of a larger lens are called "offset lenses".

... time to go, to be continued later ...
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

... Okay, I'm back ...

Now, reading this may seem strangely disorganized. That is because it is raw "stream of consciousness" content, being typed in as I explore these ideas in my head. When I write professional technical documentation, it begins much the same way, but as the content grows, I periodically go back and refactor it, by moving related things to be near each other, organized into topics that you may later find in an outline for the document. When paragraphs are moved, some sentences may be rearranged or reworded to make it simpler, less redundant, and more coherent.

But, here, this is just raw content, so you can get a feel for how I think about this stuff. Later, some of this text may become comments in source code that implements my ideas in software.

Now, back to the theory of stacked offset lenses. The purpose of stacking lenses was to map enlarge the vertical FoV so the LCD display height fills your vertical FoV, and also to stretch a narrow image, from an SBS-half image pair into, into a wide landscape image such as you see through typical eyeglass lenses, or on a movie theater screen.

In a movie theater, this is typically done with true anamorphic lenses that do not cause optical distortion. These are somewhat complex and consist of mutlipe individual lens that are stacked together, some touching (and perhaps glued together) and some with space between them. What is revolutionary about the design of the Oculus Rift is the idea of using an inexpensive high-magnification single lens, positioned close to the eye to INTENTIONALLY cause image distortion, and then to correct for that distortion using a SOFTWARE pre-warp filter. We can extend that concept to perform something similar to what an anamorphic lens does, stretching a narrow image to fit a much wider screen. Instead of complex true anamorphism that stretches evenly in a horizontal direction with no distortion, I am using a stack of OFFSET lenses to stretch horizontally, at the expense of causing distortion that will be corrected in software, much like (but different from) a Rift pre-warp filter.

In my descriptions of potentially difficult technical concepts, I like to simplify (or technically OVERsimplify) my terminology, to make my already wordy posts somewhat less wordy. Although it makes them a bit inaccurate (especially to optical perfectionists in this case), I will continue to do so if it makes my posts sufficiently accurate that they can be understood, without making them "TL;DR" (Too Long; Didn't Read). In the case of lenses, I often refer a stack of offset lenses as an anamorphic lens, even though we need to add software pre-warp to achieve true anamorphic expansion.

Now, regarding a description of how lenses work, we will think in terms of a thoretically perfect pure magnifying lens (not convex, or plano-convex, or meniscus). Something that can be simulated easily with a small intuitive computer program, in this case. For this "perfect" (oversimplified) lens, we will take the example of a 5x magnification lens such as the one recommended for DIY Rift clones.

When you look at a 1-cm wide group of pixels through this lens, it will appear to be 5-cm wide. To accomplish this, all pixels are pushed outward from the center axis of the lens, proportional to the distance from that lens center, multiplied by its magnification factor. A pixel that is directly in the center of the lens axis will not appear to have moved when viewed through the lens. But a pixel immediately to its right will appear to have moved 5 pixels to the right, and a pixel that is 10 pixels to the right appears to be 50 pixels to the right. A pixel to the immediate left of the center pixel appears to be 5 pixels to the left, 1 up appears at 5 up, and 1 down appears at 5 down. Likewise, a pixel that is 10 pixels down from the center pixel looks like it is a distance of 50 pixels down when viewed through such a 5x magnifying lens.

Now what happens if you start with a 5x lens that is 6-inches WIDE? The center 2-inches acts just like the 5x magnifier lens described above. But when you get out to the edge that is 3-inches from the optical center, pixels viewed through them will appear to be 15 inches out from the optical center. Of course, in real life, you get a lot of distortion when viewing though a lens at such a sharp angle. You have to deal with things like "Brewster's Angle" where behond that you get total reflection from the surface and no refraction through the lens. But in this "perfect" lens we do not worry about such optical complexities.

Remember that I use OFFSET lenses in my stack. An offset lens is just an outer portion of a much larger lens, with its center far from the optical center of the original much larger lens. With our 6-inch fresnel magnifiers, when we cut them into three pieces that are each about 2-inches wide, the left and right outer portions start at 1-inch from optical center and extend to 3-inches from optical center. The effect is that when viewing the LCD screen through it with your eye over the ORIGINAL optical center, it appears to shift pixels from 5-inches to the right on the left edge, up to 15-pixels to the right on the right edge. But we do use it with our eye positioned 1-inch to the left of its left edge. Instead we move it so our eye is centered over it, which probably complicates the mathematics a bit, but by observing an image on the screen it behaves pretty much as described above. Pixels in front of my nose move to the right about 1-inch, and pixels at stretch wider the farther to the right you look, with pixels all the way to the right edge of the lens (in theory, about 15-inches to the right). Disturbingly, for a pair of images where you can ALREADY see some of the left image with the right eye, that left image is pulled q-inch into the right FoV! Luckily we can add an equivalent offset lens cut from the LEFT side of the original lens, on stacked flat against this RIGHT offset lens, to stretch the image toward the left. The stretching for the left offset lens will be a mirror of the right offset lens, so that the right edge pushes pixels about 5-inches to the left, and the left edge pushes pixels 15-pixels to the left. Because we stack these two offset lenses and our eye is not over the ORIGINAL optical center, there are mathematical complications that we will not bother to predict. Instead we will observe the net results using real fresnel lenses trimmed from a fresnel page magnifier that I estimate to be about 3x magnification.

When viewing an SBS-Half image pair, with the nose over the center line and a pair of stacked 3x offset lenses (as describe above) are positioned close to the eye and parallel to the screen, the inner FoV extends well past the nose (making visible pixels where the nose should be), and outer FoV is vastly extended to. For my (near-sighted) vision, I can see borders all around the image (including part of the image for the other eye), but adding extra overall magnification pushes all borders just past the limits of my FoV (exaclty what we want). To get that extra magnification, I use the center portion of the fresnel magifiers (which actually magifies a bit too much for me but is probably about right for somebody with perfect vision). Ideally, the offset lenses should be the amount of magnification needed to not require an extra magnifying lens, but the required magnification probably depends on how much the viewer is near-sighted or far-sighted. what I did is to tape the offset lenses into my safety goggles, and then (optionally) place the extra magnifier layer on top of them, easy to be removed later. The observed result when viewed through one eye is nearly perfect coverage of the full FoV, at the expense of increased distortion extending from TWO DIFFERENT optical centers (or THREE optical centers when a magnifier lens is added to the lens stack). The pre-warp algorithm has to take all of these lens optical centers (and offsets) into account to compensate for them.

When viewing an image that has no (or incorrect) pre-warp distortion, some objects diagonally offset from the optical center may be stretched DIAGONALLY outward by different amounts, caused by parallax differences between them in the stereoscopic image pair. This results in different VERTICAL OFFSETS making them impossible to stereoscopically merge near the outer edges of the display, unless the correct pre-warp is applied to prevent mismatched vertical offsets. For the "anamorphic" pre-warp filter to match the real physical lens centers, the lenses must be measured accurately and cut uniformly, unlike the lenses that I crudely rough-cut just for experimentation.

Conlusion: Before making a software pre-warp filter, I need to construct another set of stacked fresnel offset lenses and optional magnifier, using careful measurements and uniform trimming, to exactly match my software filter. Otherwise, mismatched vertical offsets in stereoscopic pairs will cause eyestrain. With careful construction of the lens elements and lens stacks, I believe we can have a vast FoV from a single 7-inch LCD panel (as used in my Nexus 7 tablet PC).

EDIT: In another set of experiments, I used a stack of FIVE untrimmed 7-inch wide fresnel magnifiers, touching my face just between my eyes, and curved to wrap around my eyebrow and touching the side of my face just in front of my ear. The lenses were also touching the tip of my nose, and my cheekbone. When my 7-inch display containing an SBS-Half stereoscopic image pair was placed in front of my face while holding the magnifier stack in this position, I could see pixels (all in pretty good focus) in every possible direction, including where parts of my face should have obstructed my view. This was TOTAL FoV, all from a single 7-inch display, and you cannot get any better FoV than that. The only problem is that stretching half a million pixels over this large of a visual field makes the pixel density awefully low, but even so, the immersion is truly amazing, even if a bit blurred. To use TWO lens stacks, touching your nose, cheeks, and eyebrows from ear to ear, you would need a special pre-warp filter to allow stereoscopic merging, but the results would look truly amazing, and the screen is only about 1-inch in front of your nose so the full HMD would be extremely close to the face making the weight of the display less of an issue from reduced leverage. And it might look a little less "dorky".
:D
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

At this point, I would like some "peer review" feedback. How am I doing? Is this stuff interesting? Do you see any flaws in my conclusions that I reached during my experiments? Does anybody have a simple formula to calculate the pre-warp filter I will need for a stack of two offset lenses (with different optical centers) as described above? How about a formula for adding the third optional magnifier lens (with a third optical center added to the mix)? Should I try cutting fresnel lenses to stick onto the inside surface of high-power reading glasses (with meniscus lenses) so there is no third optical center to deal with, and different people can use different reading glass magnifications? Do you have any other comments, suggestions, or questions about my lens experiments?

And, really, how do you like my experimental approach and my method of describing it here? Does it help, or should I keep more of it to myself?

I need feedback, to help me decide how to spend my time here and what I should document. Thanks.

So MANY ideas, and so LITTLE time... ;)
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

My graphics experience is primarily in directly manipulating pixels in a frame buffer. I have been doing that since the days of CGA on the original IBM PC (before they even had a hard drive option). So I really feel comfortable with pushing pixels to do my bidding. One side benefit is that I can pipeline everything using custom blitters (Bit-Block Transfer functions) that can simultaneously do filtering on pixels while they are being moved. This was the only way to go on antique processors, and now it is even more important to handle data from RAM only once, while it remains fresh in modern multi-level cache. This is the best way to guarantee low latency. Passing a line-at-a-time through a series of filters is faster than passing an entire frame through a sequence of filters, especially when that frame does not fit in cache, such as when using low power processors like the Raspberry Pi.

I realize that I should use modern GPUs, but I want to start with the basics and work up from there. I always like to start with a firm but minimalistic foundation, doing a lot with a little, and then keep that as a least-common-denominator fallback position (such as software rendering).

My little adapter just came today that converts analog video to 720p or 1080p, and even a lowly PIC or AVR can output analog video with just a couple of output pins and a couple of resistors, so it would be cool to see what kind of minimal immersive experience could be had by connecting an Oculus Rift to a PIC processor.
:D

Now, I plan to start with processing raw pixels directly in framebuffers, and work up with there, for the reasons described above. One common denominator for framebuffer access that works with LOTS of different computers is SDL (Simple DirectMedia Layer):
http://en.wikipedia.org/wiki/Simple_DirectMedia_Layer

There is a ton of software out there that can use SDL, and one of them is Doom (or prboom). And OGRE can also run on top of SDL. But I plan to start with using SDL just for device independent framebuffer access.

I will show how to implement line and arc drawing, and bitmap and vector character sets (Hershey fonts) using a Raspberry Pi. That means that I should get around to ordering one soon. I like the fact that the RasPi can output video directly to HDMI, so does not need to depend on the "analog video to HDMI" adapter I just got today.

After basic vector art primitives, I will move on to bitmap graphics and procedural texturing. And then we can do the all-important displacement mapping. Why is that important? We will use simple displacement mapping to create a pre-warp filter for the Oculus Rift (and another displacement map for my "anomorpic-like" fresnel lens stacks).

A displacement map is just a bitmap image that contains colored pixels which represent how much to MOVE the "input pixel pointer" away from its normal X and Y coordinates while blitting am image from one location to another. Displacement mapping can also be pipelined into other graphics primitives (such as the ones described above) to drawing directly to the output display buffer without blitting between buffers, which minimizes latency.

A displacement image typically contains two color planes such as red and green. We can use the color value as a signed number that specifies how much to move the input pixel pointer from its normal position. For example, a color value with RED=0 and GREEN=0 would put the pixel in its normal location (no offset). A value of RED=8 would move right 8 pixels, and RED=-12 would move left 12 pixels. GREEN=23 moves down 23 pixels, and GREEN=-1 moves up one pixel from its default input position.

Using a properly constructed displacement map will warp an image in such a way that viewing the warped image though our lenses that cause warp distortion when place very close to the eye, the resulting image will appear to be totally correct. In otherwords, we intentionally warp the image so that the distortion in our lenses puts the pixels back where they should be. The pre-warp can do more than just remove unwanted lens distortion. It can also do anamorphic (asymmetrical) stretching, to convert a portrait mode SBS-Half image into a landcape mode (wide-FoV) image.

Our displacement maps can be calculated, and then adjusted empirically while viewing test patterns through our lenses until everything looks correct. For our displacement maps to work on multipe devices (such as my fresnel lens stacks) they will need to be constructed carefully so that they can be reproduced without needing custom displacement map images for each unit.

... More to come later ...
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

Regarding my thoughts about using the Raspberry Pi as a portable gaming device to be used with an Oculus Rift, here is an example of a RasPi app that I would like to port to the Rift:

https://web.archive.org/web/20130514124 ... rena?adult

Image

Image

Image

This needs to be head-tracked and pre-warped for the Rift. If the RasPi can do this in stereoscopic 3D too, all the better!

Remember that by uncoupling head tracking from rendering, we can still have (a portion of) the view track our head rotation quickly, keeping us immersively anchored in the VR reference frame, even while the game world around us updates at a slower pace. That requires rendering a larger FoV than our HMD can see, so we have some margin to look into when we move our heads a little in and out of the visible margins.

But hey, this game for the RasPi shows that we can do more with it as a Rift gaming device than just simple "90's era" VR games.
:D

And because most 7-inch tablet PCs are MUCH more powerful than a RasPi, something like this should be a "piece of cake" for a Fov2Go-style HMD add-on for a tablet PC.
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

And here is Pi3D, a 3D Python graphics & resources app for the Rasberry Pi:
http://store.raspberrypi.com/projects/skillmanmedia

Pi3D source code:
https://github.com/tipam/pi3d

Image

Image

Image

With the source code, we can add Rift (and Rift-like clone) support to Pi3D.

EDIT: I found a configuration script for the RasPi that makes it display the desktop in SBS-Half format, which might work okay with the Rift, or with a tablet based HMD (after pre-warp is added).
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Re: Fresnel lens stack for "supernatural" FoV

Post by druidsbane »

Interesting read so far. Very interested in seeing where this and foisi's HMD are going.
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

druidsbane wrote:Interesting read so far. Very interested in seeing where this and foisi's HMD are going.
It is a good thing to have multiple options in HMDs, at different price points and for different applications. In my experimental approach to HMD designs, I am using minimum cost and maximum simplicity (at the expense of image quality) as my fundamental guidelines. I think that in the tradeoff between immersion and visual fidelity, when using low cost portable computers, immersion has to come first. We can use high quality and custom optics later. I am just exploring some options in basic design concepts for now, while waiting for my Rift.
:D
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

I just did another experiment with lens stacking. This time I stacked my 6x and 5x reading glasses. Then I viewed the Oculus test image on my Nexus 7. With that much magnification, it focused closely, but not close enough. I could see a bit of both overlapped images (including part of the wrong image) and I could see the outer borders of the display.

Next, I added a pair of 3x reading glasses on top. Those have larger lenses so they fit nicely. My ears and nose managed to hold them all in place. With all three glasses (6x and 5x and 3x) stacked, the test image filled the FoV of my reading glasses, without seeing any of the borders or of the wrong image. This worked quite well. The only minor problem is that these glasses have meniscus lenses, which cause almost no warp distortion or chromatic aberration even at such close distance to the display. The pre-warp for reading glass lens stacks would need to be much less than what the Rift uses, and perhaps no pre-warp would be acceptable. That gives a much sharper display than when warping, and would be MUCH better for displaying text, such as a windows desktop. The downside is that the FoV is limited to the eyeglass frames (the same as in Real Life). Also, the pixel density is pretty much the same all over the display.

So we have FOUR options:
1) Oculus Rift, with distortion but increased central pixel density. This has support by SDK and some games.
2) Eyeglass lens stacks, with almost no distortion, with even pixel density and increased text readability. Things look curved when viewed with Oculus pre-warp.
3) Fresnel lens stacks very close to the eyes, for "anamorphic-like" (dual offset) stretching from portrait to landscape mode giving very increased horizontal FoV.
4) Extreme fresnel lens stacks curved around face, for "total" FoV, but at the expense of a lot more distortion.

All options require custom pre-warp that is different for each lens option. Fresnel offset stacks have much more critical pre-warp to prevent stereo pair vertical misalignment.

And recent experiments using the Oculus test image confirm that non-overlapped images work great (as long as you cannot see part of the wrong image). For reference, here is that image again:

Image

If you free view the above wide-eye image pair, you may want to hold a divider (sheet of dark paper) sticking from the screen (between the images) extending out toward between your eyes. That is usually not necessary with fully overlapped images, but with these non-overlapped images it is pretty important.
Last edited by geekmaster on Tue Aug 16, 2016 10:00 am, edited 1 time in total.
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Re: Fresnel lens stack for "supernatural" FoV

Post by Okta »

Can you show a picture of your lens "stack". From memory Fresnel's seems to do very little when stacked flat together without a gap between lenses. My head has a decent gap between them to get the FOV increase.

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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

Okta wrote:Can you show a picture of your lens "stack". From memory Fresnel's seems to do very little when stacked flat together without a gap between lenses. My head has a decent gap between them to get the FOV increase.
I posted photos earlier in this thread. My stacks are not all centers. And the lenses are flipped over from how you have them. I am exploiting the offset property from looking through the outer portions of the lenses, which act like prisms because they model a portion of a larger lens that is thick on one edge and thin on the other. I am stacking opposite sides of the larger lens, which is effectively the same as a DIY anamorphic lens. But because my "prisms" are cut from a convex lens, they also have some magnification and distortion (similar to that in the Rift lenses). The magnification is significant, but not what you get by spacing them apart. That is why I had to stack FIVE lenses in another design when wrapped around my face from ear to ear.

To see my photos, look back through this thread. To understand how they work, read these linked references:

Offset lenses:
http://www.hcinema.de/pdf/infocus-in72- ... set-en.pdf

DIY anamorphic prism stacks:
http://www.zuggsoft.com/theater/prism.htm

Remember, I am exploiting the DISTORTION properties of these fresnel lens stacks much more than their magnification. From an empirical point of view, it appears that stacking three 3x lenses so that they touch gives about 5x vertical magnification, but horizontally, it varies from about 6x on the left to (just estimating here) perhaps 18x on the right. The complex distortion in my lens stacks can be corrected with suitable pre-warp software, similar to that used by the Rift.

EDIT: Here is an photo of a fresnel lens stack from an earlier post (click photo for larger version):

Image

The lens stack shown above contains the left 1/3 and right 1/3 of a 6-inch fresnel page magnifier. These "offset lenses" stretch the image horizontally much more than vertically, because their physical centers are offset 2-inches to the right and 2-inches to the left of the original optical center in the center 1/3 of the original magnifier. As you can see in the photo, the corner of the lens stack actually rests on the nose piece, and actually touches my face between my nose and cheek. They sit so close to my eyes that my eyelashes slightly brush against them. I also add a third mangifying lens to the stack when using them (cut from the center 1/3 of the original fresnel page magnifier), to stretch the images evenly so I cannot see the borders. This gives a huge FoV. You can get a better idea how and where they are mounted from more photos in this post:
http://www.mtbs3d.com/phpBB/viewtopic.p ... 60#p103461

Keep in mind that viewing images that do not have proper pre-warp correction applied to them will cause steroscopic covergence problems in the outer areas of the image, but the image center and low-parallax areas with distant objects look pretty good. Just know that the images CAN be corrected in software, and pay most attention to WHERE you can see all those pixels. I still need a way to mount my 7-inch display (tablet PC, or LCD panel) in front of the safety goggles at the right distance, which as I recall is no more than about two inches (or less).

This is a difficult concept to understand, and it is really important to actually try it yourself to see how it works. Photos and descriptions alone are not adequate. I intentionally used parts you can get at a local dollar store (or hardware stores and book stores), just so that you CAN duplicate my experiments quickly, easily, and inexpensively. Just DO it!

Enjoy! :D
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

Here is a simple "thought experiment" to show how an offset lens works:

1) Imagine a video projector is projecting a movie onto a movie screen.
2) Adjust your video content so that everything of interest falls into the right 1/3 of the screen.
3) Place a sheet of cardboard in front of the projector so that it casts a shadow on left 2/3 of the movie screen.
4) Remove the portions of the lens and video content that are not putting pixels onto the screen.

As you can imaging, the image on the screen is offset far from where the projector appears to be pointing.

5) Now slide trimmed offset lens portion in the projector so that image on the movie screen also slides, back toward the center of the FoV.

Because the offset portion of a lens behaves as a curved prism, it will stretch the image horizontally after you slide it as describe. It will also add chromatic aberration just like when viewing a rainbow cast by a prism. Because this offset lens combines features of a magnifying lens and a prism, the resulting image is stretched outward away from the original lens optical center.

6) Take another offset lens cut from the other side of the original lens, and place it in front of the first offset lens.

This has the effect of partially correcting for the other lens distortion, but in a nonlinear fashion. The net result is that the image is stretched most on the outer left and right sides, and somewhat less in the center. This is exacly what we need to combine anamorphic stretching with the non-linear stretching used to our advantage inside the Rift Dev Kits, plus an anamorphic effect that lets us stretch a portrait mode SBS-Half image horizontal to much more of our available FoV, without also stretching vertically which would waste vertical resolution by pushing onscreen pixels well beyond our vertical FoV.

As mentioned previously, the relatively low resolution of available displays at this time makes this a tradeoff between resolution, central pixel density, total FoV, pixel distortion, and chromatic aberration.

Ideally, we would have high quality meniscus lenses (magnifying reading glasses) that can focus on a display screen just one inch or so from our faces, and much higher screen resolution, so we can (mostly) eliminate the need for pre-warp correction.
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Re: Fresnel lens stack for "supernatural" FoV

Post by omeDev »

could this potentially ruin our eyes? could the rift alter our vision in some way or another? staring inside the rift frequently.. is it a bad idea?
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

omeDev wrote:could this potentially ruin our eyes? could the rift alter our vision in some way or another? staring inside the rift frequently.. is it a bad idea?
There are other potential risks that may be more important than potential eye damage or other potentially harmful vision alterations. Mind and body alterations are more likely. But increased exposure to new ideas and rich rewarding content, coupled with increased exercise from head and body tracking, would all be good. Bad content exposure is more of a concern.

There is a risk of PTSD for repeated extended sessions of extremely anxious immersive content, especially with aversive haptic feedback (like annoying electric shocks). Too much exposure to violence may also desensitize us, or alter our perception of reality (especially when accompanied by sleep deprivation). Some content may be subliminally suggestive influencing what we purchase of who we vote for. But regarding potential physical alterations, optical misalignment or incorrect pre-warp may cause eyestrain. Normal usage should be no worse than watching 3D TV, unless turning your head quickly while wearing the extra mass on your head causes you neck strain, which is more of a physical fitness problem than anything.

Some people are also concerned about uncoupling focus and stereoscopic convergence, but I have been viewing 3D content for extended periods for many decades, including free-viewing cross-eye (and later wide-eye) stereoscopic images, and I think practice just makes it easier, so that is a GOOD thing IMHO.

I am not a medical professional, so you must do your own research and make your own risk assessment when deciding how much time to spend in VR, and what equipment to use, and what content to consume (and to create).
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Re: Fresnel lens stack for "supernatural" FoV

Post by omeDev »

I was reading VR related materials but I felt lazy and uhh... lol for better or worse I'm actually hoping for the rift to be "that" immersive.
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

omeDev wrote:I was reading VR related materials but I felt lazy and uhh... lol for better or worse I'm actually hoping for the rift to be "that" immersive.
There is another risk I did not mention. If you make a habit of "losing your lunch" while wearing the Rift, you could starve to death...
:woot
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

I took out a Rift lens cup, and mounted a fresnel lens stack in its place. Part of the larger FoV it gave me was obstructed by the eye holes that the eyecups mount against. I would have to cut those holes larger (and probably square) to get the full FoV that I experience when using these fresnel lens stacks with a 7-inch tablet PC with no obstructions.

So in this case, fresnel lenses give no benefit without cutting off bits of my Rift, and I am not ready to do that yet.

Fresnel lens stacks are still a great idea for use with an unobstructed panel, such as in a DIY Rift clone. They do require different pre-warp distortion though, as mentioned in previous posts.
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Re: Fresnel lens stack for "supernatural" FoV

Post by remosito »

while looking around for fresnel lens info on the web I came accross this one:

One Fresnel Lens maker at least seems to be at the LightFair 2013 exhibition at the Philadelphia, PA Convention Center, April 23-25, 2013.

http://www.fresneltech.com/ is the manufacturer. http://www.lightfair.com is the show.

maybe this is of interest to somebody in the Philly Area. I know I would go if I'd live close there :-)


cheers

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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

remosito wrote:while looking around for fresnel lens info on the web I came accross this one:

One Fresnel Lens maker at least seems to be at the LightFair 2013 exhibition at the Philadelphia, PA Convention Center, April 23-25, 2013.

http://www.fresneltech.com/ is the manufacturer. http://www.lightfair.com is the show.

maybe this is of interest to somebody in the Philly Area. I know I would go if I'd live close there :-)


cheers

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I got some polypropylene fresnel lenses from fresneltech.com that work GREAT for thermal imaging, and are MUCH cheaper and more durable and more light weight than other thermal infrared lense. You can see a nice "hot and cold" video on this page, demonstrating their super cheap fresnel thermal imaging lenses:
http://www.fresneltech.com/thermalimaging.html

They have a $100 minimum order, so I requested (and received) some free sample lenses. ;)

They put a lot of research and engineering into their high quality lens designs, and I would highly recommend their optical grade products as well.
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Re: Fresnel lens stack for "supernatural" FoV

Post by remosito »

geekmaster wrote:I got some polypropylene fresnel lenses from fresneltech.com that work GREAT for thermal imaging, and are MUCH cheaper and more durable and more light weight than other thermal infrared lense. You can see a nice "hot and cold" video on this page, demonstrating their super cheap fresnel thermal imaging lenses:
http://www.fresneltech.com/thermalimaging.html

They have a $100 minimum order, so I requested (and received) some free sample lenses. ;)

They put a lot of research and engineering into their high quality lens designs, and I would highly recommend their optical grade products as well.

Good to know that :-)
In a post on page 2 you wrote:
I would love to find a custom lens that provides both left and right offset and required magnification in a single lens. If you can find one, please let us know. I am interested in good quality fresnel lenses, and in affordable solid aspheric anamorphic lenses (for better image quality).

Did you by any chance contact them about such a single lens and how much it would cost? Maybe they could even make a wraparound version you drew on page 1?
This would have been my motivation to visit that lightfair...

Forgive me if having custom one lens solution sourcing has already been covered. Still only on page 2. Massive amount of info to read and digest!
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Re: Fresnel lens stack for "supernatural" FoV

Post by remosito »

Holy cuacamole,

this thread was the most exhilirating and intense tech read of my life. :woot

Thank you!

It as well beats George Martin and his Song of Ice and Fire books on most hc cliffhanger!

What happened with the pixelpushing and working out the pre-warp for your setup? How is the final experience? ;-)

would really love to know how the story ends and if there is a happy end

:hatsoff and :bow
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Re: Fresnel lens stack for "supernatural" FoV

Post by zalo »

Somehow I've managed to completely miss this thread for the last two months :x

I have some lenses on the way from 3dlens.com, but if I had known what you meant by "offset" lenses, I would have gotten some fresnel bookmark lenses as well!

Do you think these are wide enough to give a good "offset" effect: http://www.3dlens.com/shop/bookmark-mag ... l-lens.php ?

Also, are the two offsetted bits cut equidistant from the optical center of the lens, or is one lens in the stack more offset than the other lens?

Thanks for your research!
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

zalo wrote:Somehow I've managed to completely miss this thread for the last two months :x

I have some lenses on the way from 3dlens.com, but if I had known what you meant by "offset" lenses, I would have gotten some fresnel bookmark lenses as well!

Do you think these are wide enough to give a good "offset" effect: http://www.3dlens.com/shop/bookmark-mag ... l-lens.php ?

Also, are the two offsetted bits cut equidistant from the optical center of the lens, or is one lens in the stack more offset than the other lens?

Thanks for your research!
I do not know about that particular lens without trying it. I cut the lens portion into 3 equal-sized sections (not counting the non-fresnel borders). The outer two sections are offset, because their optical axis is through the (missing) center section. Cutting a lens does not change its optical axis (original center in this case). Looking through one side or the other pulls the image that direction, more as you get farther from the center. Stacking two of them stretches the inner and outer sides out much more into your peripheral view, BUT that stretched image has much less pixel density than the screen center. I plan to try fresnel stacks with my iPad3 displays.
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Re: Fresnel lens stack for "supernatural" FoV

Post by WadeWatts »

@ Geekmaster

When I am not in the Oasis I follow this thread closely. ;) I have an iPad 3 and I am by profession an iOS developer who also has Unity3D experience. My Rift is on the way :D and I am developing a VR experience specifically for the Rift. :woot

This thread caught my eye and somehow in the process of developing for the Rift I have become obsessed with the DIY HMD VR scene and hacking the Rift.

I ordered an iPad display for experimentation to see if I can squeeze some wider FOV and higher quality pixel density on my own. I hope to be able to contribute to this thread as soon as my parts arrive. I see you are now starting to play with the iPad 3 display! Cool!

I already have 4 lenses using the "LEEP" method and now I will play with Fresnels. If you need any help just let me know. Love this thread.
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Re: Fresnel lens stack for "supernatural" FoV

Post by mickman »

Interesting read...
I am thinking.. could I experiment with an LCD Viewfinder Magnifier such as the one on my Canon EOS camera.. ( a rubber LCD viewing hood )

Remove the rubber hood & attach a modified fresnel lens to each side of the glass might allow me to experiment with a siilar wide horizontal fov.. yes ?

Image

I have tried pulling the glass lens from the rubber hood & looking through it close to a 6" image & am really amazed how incredibly focused and large the image becomes.... I hold the lens approx. 2.5 " from either an iPad3 or iPhone5 screen.
So simply ordering a couple of plastic fresnel lenses and experimenting ... I might be able to come up with a similar setup as described by GeekMaster... yes ?
Image Image

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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

Mystify wrote:I like the hybrid lens concept. That seems like it has potential.
Especially now that the Crescent Bay (and perhaps CV1) have dispensed with solid lenses and are reported to be using hybrid lenses. Sadly, the USPTO is claimed to not trust web content posting dates, prefering to only use other patents as prior art. And the "patent reforms" changing "first to invent" to "first to file" gives patent trolls preferential treatment over inventors. What kind of "reform" is that?

Also, I heard about recent patent filings on curved fresnel lenses even though that is how the original fresnels were created in the early days (taking a solid planar lens and grinding concentric flat cylinders out of the flat backside, hollowing it out into a curved fresnel lens). Grinding prismatic rings into a flat lens was perfected later, with angle adjustments needed for relocating the curved surface down into the flat planar zone.

Interestingly, I have been playing with fresnel lenses these past several months that allow me to see pixels on my Galaxy Note 4 screen out of the corner of my eye every direction I can look, including where my nose and eyebrows and cheeks should be), and sharp everywhere too. They are curved so they touch skin all around my eye just like in the image I posted far above (next to my nose, under my eyebrow, and above my cheekbone). Though screendoor effect is a factor, I prefer the supernatural FoV (270-degrees or so) even at the expenses of SDE. Like Eric Howlett said, we just need to DEFOCUS a little bit to minimize SDE (the best focus for VR is not the sharpest focus). Of course, we may need to trim the lens edges to fit the facial profile of each user, and I used a depth camera to digitize my facial depth map for that lens trimming operation. I envision getting custom trimmed lenses to be similar to getting new eyeglasses at an optical shop, where your face is scanned for lens edge contour before trimming curved lenses to hug your face.

It seems that many HMDs are abandoning their prior solid lenses in preference of the ideas proposed in this thread. The sincerest form of flatter, eh? Though getting a little credit is preferred over filing patents, though lawyers and investors hate the liability potential of sharing credit. I just hope nobody tries to prevent ME from using my own private research and development.

I was asked by associates to keep my personal lens "IP" quiet, but I am not legally bound by such requests and I no longer keep such nonbeneficial company. I have additional research for simple DIY "lightfield" lenses, which work amazingly well regardless of eyeglass prescription, with no lenses needed between your eyes, the lightfield lenses (also touching skin all around), and the display surface at any distance. For testing, I laid back with a tablet screen face down balanced on my forehead and nose, and I could focus clearly on subpixels with my curved lightfield devices laying over my eyes. Amazing experience. And they let me see clearly up to infinity too, when looking out the window at distant trees.

I want to complete these things so I can release them, but there are many other things above them on my "To Do" list. I need a team of developers to help me with all my unfinished projects that others have told me are awesome. Now how do I do that?
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Re: Fresnel lens stack for "supernatural" FoV

Post by Dilip »

geekmaster wrote: want to complete these things so I can release them, but there are many other things above them on my "To Do" list. I need a team of developers to help me with all my unfinished projects that others have told me are awesome. Now how do I do that?
You very much know the answer, approach right Venture Capitalists show them potential at private showdown, hunt for talent in market or may be here. Take some interviews, assign the task to your chosen,mentor & supervise them... then monetize the results by setting a corporation and save some for further R&D.

There can be other way but harder one, that's you do all then ....Monetize the results or post them for free (here/some where) latter doesn't make sense unless you are Warren Buffett rich. Till we are in world, we all need funds. :)
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

And BTW, my latest iteration uses single lenses that work much better than those stacks in this thread (which I used only for increased magnification from dollar store lenses). They key (as I mentioned) was and is lens offset. I have lenses that give me more than 180-degree FoV on my Galaxy Note 4 display. Live pixels as fas as I can see out of the corners of my eyes, even with then turned painfully sideways. The key is curved lenses exactly as I showed in a diagram earlier in this thread.
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

This post has an image of my idea I finally protoyped:
http://www.mtbs3d.com/phpBB/viewtopic.p ... 373#p99408

It showed a curved lens on one side (as if a ping-pong ball shaped lens were cut to fit snugly under the eyebrow, along the nose, and against the cheek).

Here is that image again:
Image

My prototype lens is segmented like a Buckyball (glued lens pieces), but I plan to make a smooth-curved lens (If I live long enough). Even the segmented lens demonstrates the awesome potential of what I have developed here (if Oculus doesn't patent it to require an expensive "prior art" battle, like they did with my PTZ Tweening ideas).
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Re: Fresnel lens stack for "supernatural" FoV

Post by cadcoke5 »

I suspect that the final result of the supernatural fov is not really any different than the kind of image you get from a fish-eye lens. I also suspect that your brain will not interpret the extra FoV as coming from outside its normal range, but rather will try to process the objects outside of the normal range as being inside the normal range. In other words, your mind may get a distorted "map" of where things are.

However, other than the areas blocked by the nose, the extra area is in the peripheral vision area. Which is not really very detailed. It is more about detecting motion. So, the issue of the brain mis-mapping those objects may not be a problem.

Of course, all this is pure speculation, and sometimes the world does not comply with our imagination!

-Joe
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Re: Fresnel lens stack for "supernatural" FoV

Post by geekmaster »

cadcoke5 wrote:I suspect that the final result of the supernatural fov is not really any different than the kind of image you get from a fish-eye lens. I also suspect that your brain will not interpret the extra FoV as coming from outside its normal range, but rather will try to process the objects outside of the normal range as being inside the normal range. In other words, your mind may get a distorted "map" of where things are.

However, other than the areas blocked by the nose, the extra area is in the peripheral vision area. Which is not really very detailed. It is more about detecting motion. So, the issue of the brain mis-mapping those objects may not be a problem.

Of course, all this is pure speculation, and sometimes the world does not comply with our imagination!

-Joe
Any mismapping can be compensated with a correct pre-warp -- just put the pixels where your brain expects to see them. My testeing shows that this works quite well in practice. But it will depend on face shape, so must be adjustable. You really can see live pixels where facial parts would normally obstruct, due to lensing between your eyes and facial obsctructions -- lens right to the skin all around.
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Re: Fresnel lens stack for "supernatural" FoV

Post by cadcoke5 »

My comment about distortion was in thinking that some of the retina is receiving images from an area where it would not normally have originated. Is that what you are hoping to do?

I can imagine that there are areas that are sometimes exposed to light when you look to one side, and then those areas are blocked when you look at the other extreme. The nose would be the main area. However, I suspect the brain has learned to ignore the nose, and simply relies on the image from the other eye to detect what is going on in that direction.

I will mention something else I have read. (sorry I don't have a source). There was a study on the flexibility of the mind to deal with the images we receive. Volunteers wore prism glasses that turned the world upside down for a week or two, non-stop. They were able to successfully train their brain to deal with that, so that when they finally removed the glasses, they felt that the non-prism view was upside down. They adjusted back to normal vision quicker than they did to the prism glasses, but it still took some time.

So, even if it possible to train your brain to accept hyper vision, perhaps even 360 deg vision, I would be concerned that the ability to switch back to normal mode may be a problem. But, perhaps it is viable to train your self enough that you can switch between the two on a moment's notice. It wold be wise, however, to study this process very well before attempting to use a car. A failure to use the correct "vision mode" may be fatal to yourself or others.

By the way, there is actually a type of "hyper vision" used by people with tunnel vision caused by the loss of their peripheral vision. They can use special glasses to bring more of the peripheral area into their remaining area of vision. There were actually several variations of the idea. I just did a quick search and found one study that had some success, but it was certainly not a slam-dunk.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2867070/

-Joe
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