Question about collimated display systems.

[mikesblack]

Hi Wayne,

How wide, radius and degrees vertical and horizontal will the final mirror be?

Given that material can be found at 55 inches, could you remind me what limits we face and in my case assuming a 7 foot radius curve and 40 degrees vertical( ideal).

I have been thinking about using either thin plasic packaging tape or mylar tape to join 2 sheets of mylar. I have experimented with small pieces and have found good results. The tape is applied on the back of both pieces and carefully lined up and smoothed on.

Love to hear your thoughts on that.

Hope you and Gene are well.

[geneb]

mikesblack: I suspect that when you try to stretch the mylar under vacuum that it's going to distort at the seams.

The current setup gives us an 8' diameter mirror. The framework provides 180 "real" degrees of mirror plus the extra we get for the "ears". If I remember correctly, this gives us 180 degress of "perfect" view with some space on either end that provides "usable" mirror which then degrades into "funhouse mirror" at the ends.

If you look at this picture: http://www.fotothing.com/photos/492/4920602806627da215d989d52150212c_ab4.jpg you'll see the "ear" that we keep referring to. On their setup, they've trimmed the mylar back from the full curve of the ear. Our mirror will cover it completely because of how we're attaching it.

The photo that really got my attention was this one:
http://www.fotothing.com/photos/115/1155484a84e6e1cf582dfeb1bbc9a914_9f6.jpg
If you zoom in on it you can see that the mylar is being brought into position in a fashion very similar to how a shower curtain is hung. You can also see two black parallel lines at the top edge of the mylar. This makes me wonder if there's something sewn into the material - maybe a reinforcing strip or something like a sail bat?

I suspect that band is some kind of reinforcement for the method they're using to hold the mylar in place. I'd love to talk to the guy on the ladder. :)

That image shows some of very interesting details - one an approximate depth of the frame. You can see it in the bottom right hand corner of the image. Another detail is what appears to be the vacuum port at the back of the framework in the center. I'm not sure why there is two - volume maybe?

In the lower LEFT corner, you can see what looks suspiciously like the paper that would cover double-sided tape! It looks like the repeating logo thing done on some brands of 3M tape. The tan color above it may also be some kind of tape backing. If you look closely, you'll see a "hump" in the material (right near the left edge of the image). I've seen a similar effect in double-sided tape backing when it's applied around a curve... I bet if we could see the "ear" on that end, there would be a line of that material going straight up to the top edge of the framework.

In this image:
http://www.fotothing.com/photos/88d/88dc8c4ee45058bf44ca4f520cc2e7fd_15d.jpg

...HA! I was right! If you look at the bottom of the image, just to the right of the ladder, you can see a bit of adhesive covering peeking from behind the mylar and directly to the right of that there is an obvious band where the mylar is stuck to the tape! I don't see any evidence of the reinforcement band on the bottom, so that may have only been done in order to lay the mirror in place before they expose the adhesive behind it. In fact, if you look to the top of the mirror directly above the band I just mentioned, you can see extra material folding forward of a line that appears to have attached it - I think at this point in the process the worker is working from right to left - you can see how the mylar is "stiffer" on the area on his right. He's in transit on the ladder by the position of his foot, but I don't know if that's going up or down. :D The area to his left is still being supported by the top edge, so there may be some kind of rail up there that we can't see - maybe for removable clips that are attached to that reinforcing band?

This weekend I'm going to try to get the base platform built and painted. This is what the table will attach to and then the mirror chassis will attach to the table.

We're going to build a new screen - more in line with the current design. The trick is going to be building a jig in order to cut the foam with. I don't expect it to be much of a problem though. Anything that keeps my fingers way from that table saw blade makes me happy. The last one we built was something like 40+ cuts on the table saw with the blade run all the way up and my fingers about an inch away from it. I was really, really glad to be done with that particular part of the project. I had to be lucky every single time. The table saw only has to be lucky once. :)

g.

[geneb]

I just did a bit of research on the CAE 7000 Series simulator that those pictures show - it has a FOV of 200 degrees wide by 43 degrees high. The mirror that Wayne & I are building is really close to that 180-190 (or so) wide and 40 high. Not too shabby for a couple of sim geeks. :D

g.

[wledzian]

Mike,
Without digging into interference issues between cockpit and display geometry, I can squeeze about 115° out of the full-height mirror, with possibly an additional 10°-15° usable in each ear, using a 1" margin. This does not account for the dead band, which probably eats up about 5° at the top and bottom, leaving ~30° usable. If I increase the vertical FOV to give a 40° usable area, the full-height section drops all the way to 30° horizontal, perhaps 70° total including the ears.

[mikesblack]

Thank you Gene and Wayne. Appreciate the response.

What do you guys think of my idea for joining mylar in order to get full width?

[wledzian]

The seam will be locally stronger, and will therefore stretch less. This will most likely produce some fairly severe distortion.

[mikesblack]

I was thinking the same thing, but figure it may be worth the experiment. I'll let you know what I find.

BTW Do you know who manufactures the mylar for CAE and the other sim manufacturers?

[tomenglish2000]

Hello all.

I was talking to a friend who visited the install of one of these. He says that the back of the dome is a material like felt or fine carpet which is either attached to a solid structure or has been treated to be stiff enough on the back to hold the spherical form. Because its carpet/felt it isnt air tight and allows air to be drawn through it. Looking at the pictures I think he might be correct, it certaintly looks like it has hand prints in it like you would find on the top of a pool or snooker table. He didnt mention how the mylar was attached to it but I think we can see it in the pictures and figure it out.

Please look closely at this photo http://www.fotothing.com/photos/115/1155484a84e6e1cf582dfeb1bbc9a914_9f6.jpg that Gene also linked to.

Around the top and bottom of the black dome area where the mylar gets attached if you allow your eyes to follow it around the curve I believe it is sloped backwards from the black dome. Some of the patents linked earlier in the thread (if memory serves, perhaps they were on one of Mike's tutorials) showed methods for attaching the mylar. One showed the use of material to for a uniform curve around the top and bottom of the mirror so that the mylar isnt going around a sharp angle and this makes sense with the picture's sloped back attachment area.

So contrary to Gene I think the material is folded back and not forward in the second picture.
http://www.fotothing.com/photos/88d/88dc8c4ee45058bf44ca4f520cc2e7fd_15d.jpg
I also think he might be working out from the centre to the sides.

So my interpretation is this. The mylar is placed in the dome shape. Note that there is no measuring equipment visible in any of the photos (tape measures etc) so the black lines on the top must make sure the mylar is positioned correctly. As the guy moves out from the centre he removes a bit of the backing paper from the tape (as can be seen at the bottom in the second picture, there is a tail of the brown backing paper peeking out from under the mylar) and he sticks it down on using the black marks for guidance. The thing I cant figure out is how he knows where to stick the bottom, there are no black marks that I can see, surely it has to be more scientific than just guessing when the mylar is loose enough.

In the second picture at the very top right you can see the black marks for the top but on it's back there is no evidence of reinforcement.

Anyone have any thoughts?

Tom

[andyb]

I'm not sure of the exact supplier (it was 10+ yrs since I was playing with Mylar) but I do recall the manufacturer was in Eastern Europe (narrows it down slightly) and material had to be purchased by the tonne/ton or 500m +. Basically a complete roll. Even when working for a large sim company, the dollars were large.

For those currently building with Mylar, there were a few occasions when people had dropped screw drivers from the top of the screen ..... followed by a big POP and a large OH **** and then a few more OH ****'s.

The developments forward in this area is truly amazing.

Hopefully helpful:
http://www.rockwellcollins.com/~/media/Files/Unsecure/Products/Product%20Brochures/Simulation/Visual%20Display%20System/Cross%20Cockpit%20data%20sheet.aspx

[Efe Cem Elci]

Especially with the vacuum considered, even a screw might have unwanted effects (read return to square one) on the "mirror".

[Snovadnb]

http://www.youtube.com/watch?v=Wqq4-XC5f8U - You see this!?

[Snovadnb]

http://www.youtube.com/watch?v=Wqq4-XC5f8U - You saw it?

[sacad]

hi everybody ..
i've been trying to keep up with new stuff , and found my self reading the whole thread .. this is the most interesting topic of all :)
i made a solidworks prototype based on some hypo dimentions ..
5088

[arnolde]

wledzian, geneb,
It's been a couple months now since your last post, how is the wide mirror doing?
Hope you are continuing with your fantastic success :-)

regards,
Ethan

[geneb]

Sorry guys - take a peek at these videos:

http://www.youtube.com/watch?v=j3FvFx9z2R8
http://www.youtube.com/watch?v=Bx5eb5yTDQw
http://www.youtube.com/watch?v=_cyJIGII6JE

The display system is essentially completed. The vacuum controller has been rebuilt and is working perfectly. The last "construction" that needs to be done involves building a cardboard "blackout cap" to enclose the display.

g.

[arnolde]

Really amazing guys. I wish I'd been as resourceful 5 years ago when I was trying very hard to come up with a wide visual.

Could you post the mechanical dimensions of your mirror frame please?
Also, I wonder if you can see the front projection screen in night scenery? (since it's white, does it reflect ambient light?)

[wledzian]

It does reflect ambient light, but the entire assembly will eventually be capped. Ambient light shouldn't be an issue.

[arnolde]

I was thinking that even when it's fully enclosed, the few bright dots of light that are projected onto the screen at night might stray around enough to cause enough ambient light to make the screen body visible. A Sim engineer I talked to once told me thats one of the reasons that usually back projection is used. Not that that would stop me wanting one :-) I light daylight scenes better anyway!

[wledzian]

rear-projection also has its problems - light from any point on the back side can spill light on the rest of the screen, reducing contrast. The problems you mention are just as much of an issue on first-surface projection as well.

[presse55]

Hello

I'm glad I found this thread. I find this topic fascinating and am working to improve my understanding of the optics involved.

Following wlzedian's earlier post (ex. #58 ), I developed an excel spreadsheet to calculate points on a surface screen for a hypothetical collimated display. Using the resultant points, I am able to develop a very close fitting ellipsoid (major axis is horizontal, center is same as mirror, rotation axis is vertical also through center of sphere).

What I get are parameters (a,b) for the ellipse as shown here

http://www.flickr.com/photos/alfredetlaura/6032314024/

What puzzles me now is:
From the (pilot's) eyepoint, how much vertical and horizontal movement still provides an image reasonably free of distortion? In other words, how can I assess what I will see as my head moves from sided to side, or up and down? Any distortion?


Mike.Powell writes (post #78 ) something I do not understand:
"Once you have a workable configuration, you can ray trace diverging paths from multiple points on the screen surface to check for collimation accuracy."

I'm not sure how to go about doing this 'in 3D'. I can hardly immagine doing these calculations manually. I am under the impression that to answer this question, 3D ray tracing is probably required, but I'm at a loss as to how to go about doing this. I am not familiar with TurboCad.

Any pointers are well appreciated!

Ron,


On a side note:
In astronomical telescope design, a similar problem arises with the so-called tilted component scopes, such as the Schiefspiegler; with these scopes, there are two spheric reflecting surfaces tilted with respect to one another. In telescope design in general, ray traces and spot diagrams are done for two perpendicular planes: the tangential and the sagittal planes. This is well explained in Telescope Optics - Evaluation & Design, Rutten & Venrooij, Wilmann-Bell, 1988.

I'm left wondering if methods used in evaluating tilted component telescope design can be used in collimated displays.

[presse55]

Hello

I'm glad I found this thread. I find this topic fascinating and am working to improve my understanding of the optics involved.

Following wlzedian's earlier post (ex. #58 ), I developed an excel spreadsheet to calculate points on a surface screen for a hypothetical collimated display. Using the resultant points, I am able to develop a very close fitting ellipsoid (major axis is horizontal, center is same as mirror, rotation axis is vertical also through center of sphere).

What I get are parameters (a,b) for the ellipse as shown here

http://www.flickr.com/photos/alfredetlaura/6032314024/

What puzzles me now is:
From the (pilot's) eyepoint, how much vertical and horizontal movement still provides an image reasonably free of distortion? In other words, how can I assess what I will see as my head moves from sided to side, or up and down? Any distortion?


Mike.Powell writes (post #78 ) something I do not understand:
"Once you have a workable configuration, you can ray trace diverging paths from multiple points on the screen surface to check for collimation accuracy."

I'm not sure how to go about doing this 'in 3D'. I can hardly immagine doing these calculations manually. I am under the impression that to answer this question, 3D ray tracing is probably required, but I'm at a loss as to how to go about doing this. I am not familiar with TurboCad.

Any pointers are well appreciated!

Ron,


On a side note:
In astronomical telescope design, a similar problem arises with the so-called tilted component scopes, such as the Schiefspiegler; with these scopes, there are two spheric reflecting surfaces tilted with respect to one another. In telescope design in general, ray traces and spot diagrams are done for two perpendicular planes: the tangential and the sagittal planes. This is well explained in Telescope Optics - Evaluation & Design, Rutten & Venrooij, Wilmann-Bell, 1988.

I'm left wondering if methods used in evaluating tilted component telescope design can be used in collimated displays.

[beermonster]

Well as a person that didn't know anything about collimated display systems until yesterday let me say I'm all excited and the Mrs has given me the go ahead to build one, so long as it's a two person set-up. Here are a few dumb questions and cross referencing from different industries.

1) Does the mirror have to be 100% reflective? Of course you want the best you can afford; but where is the middle ground? My first projector used a white wall and then a bed sheet, so I can accept a lot of imperfections along the way.
I've been following this guy who tries a lot of diy mirror configurations for solar power and he as made a few nice looking easy(ish) to make parabolic mirrors. As we only want a portion of the mirror it looks feasible. http://www.youtube.com/watch?v=St-0HWKAY4k
http://www.youtube.com/watch?v=MYC7HyKbkpI

1b) As they do with telescope mirrors . If you attached a lot of control points on the back of a steel mirror could you pull it into the shape you wanted and correct and fine tune the image digitally. I've been looking at a lot of Johnny Chung Lee work and this could be set up to auto correct the image you want to see. http://johnnylee.net/projects/thesis/

Getting rid of the huge mirror idea. I understand why don't you project on to a white screen as it helps the illusion to bounce one image off another S0 -
2) It is possible to use a projector to project on to a mirror and have that image bounce of a white background into the eye? I just thought you could inflate a mylar balloon easier. I guess the balloon could be over sized and the holding frame would make the mylar bulge and deform where needed. You could even inflate the ballon to full a much easier to make acrylic former.

Just my ideas. Are there any CAD plans for building this. I haven't understood the maths to make one yet.

I've also though about using corian as a surface to project on to OR apply a mirror finish to.

Thanks for a good weekend of reading.

[Papa#1]

Hello,
Im very new to everything. I guess you can call me a (newbe). I need help on getting my game to work. I have eyefinity six video card and tryinbg to run six monitors. If can give any advise please let me know.

Thanks!!!
Papa#1

[jackwall]

Papa #1 ....

A couple of google search links to start you off ....

http://www.tomshardware.com/forum/276654-33-heck-eyefinity

http://www.devhardware.com/forums/ati-video-card-20/how-to-set-up-eye-infinity-310385.html

http://forums.whirlpool.net.au/archive/1469262

There is a load more on the web and I recommend some surfing and reading ......

It's kinda difficult to help when the problem is such a broad one. Exactly what problems have you encountered so far. Like, do you need help with physical installation or with configuration after your physically connected in the new card.

Try being a little more specific in the help you need and typcially someone on here will offer.

Also, this is a thread that is about Collimated Displays so it may be appropriate to start your own thread for your question !!!

Good luck
rgds

[Papa#1]

Thank you for the message. I will see if any of these may be helpful to work with. My can turn on the game just fine. It will let me up until the point I go to fly. Then the screens all go black then start flasking. The game will then shut itself down. I can't figure out why? Any suggestions?
Papa #1 ....

A couple of google search links to start you off ....

http://www.tomshardware.com/forum/276654-33-heck-eyefinity

http://www.devhardware.com/forums/ati-video-card-20/how-to-set-up-eye-infinity-310385.html

http://forums.whirlpool.net.au/archive/1469262

There is a load more on the web and I recommend some surfing and reading ......

It's kinda difficult to help when the problem is such a broad one. Exactly what problems have you encountered so far. Like, do you need help with physical installation or with configuration after your physically connected in the new card.

Try being a little more specific in the help you need and typcially someone on here will offer.

Also, this is a thread that is about Collimated Displays so it may be appropriate to start your own thread for your question !!!

Good luck
rgds

[Salire]

I've read this thread now about 3 times, and am totally fascinated. It's incredibly impressive and I'm seriously thinking about taking it on myself. But the thread died abruptly last year. Wayne and Gene, did you get done and now are having too much fun? Any updates? Lessons learned?

Thanks,

Salire

[geneb]

Salire, if you head over to http://www.youtube.com/f15sim, you can see the most recent videos that we've done on the project.

More exciting news will likely be posted this coming weekend. :)

g.

[Salire]

Thanks, Gene. Yes, I've seen all your videos, read your site, downloaded the patents, etc. The size of your rig looks doable for the space I have available (first time I've ever had a rumpus room and I want to take advantage of it). So before I start on something I'd sure love to be able to stand on your shoulders and learn from the experience.

I'm curious, too, about your personal assessment on the marginal benefit (in terms of immersive experience) of having the collimated view over a simpler wrap-around direct projection (dome or cylinder)?

Sal

[geneb]

The benefit of collimated vs a direct projected screen is HUGE. You get a sense of depth that simply isn't possible with a "normal" projected screen. The visual cues you get are as close as possible to reality - this is why the FAA mandates collimated displays for Full Flight Simulators.

Wayne can tell you much more about how he experiences the visuals than I can - I don't have binocular vision (my eyes don't work together, they work individually, so I have no "built-in" depth perception).

You should keep in mind that the display project we've built is really only suitable for a single seat cockpit - it's not large enough to do a proper two place cockpit, even a small one like a Cessna 152.

g.

[Salire]

Thanks.
re: Single seat: Yes, that's one reason I'm so attracted to the scale of your project. I'm planning a single seat GA configuration with a glass cockpit. The first try is going to be X-Plane with a FlyThisSim G1000 avionics emulation controlled by an ACER 24" touch screen, and the CH products HOTAS control suite. I'm basically going for state of the art high performance GA VLJ or Cirrus type design, but generic. I want a realistic flying experience, but I'm not driven to make it a replica of anything. In fact, I enjoy playing with the ergonomic design aspects. The OTW experience is a big deal to me, so I'm really wanting to do something that delivers. Sounds like the size of what you guys did is perfect for my application. Once I get the OTW display set, then I would build the cockpit accordingly to make the pilot view fit with the display limits.

S

[wledzian]

Salire, the increase in immersion really is one of those things that has to be experienced to be believed.

When the mirror is drawn down just enough to get rid of most of the wrinkles, an image is formed at a little more than the total path length - that is to say, if the mirror is 4 feet from your eyes and the screen is 2 feet from the mirror, the image feels like it's a little more than 6 feet away or so. This is probably similar in feel to a large 'normal' screen.

As the mirror draws down to its proper position, the image formed becomes far away, and it feels far away. It no longer feels like you're looking at a screen; Your eyes relax and focus off at a distance, as if you were looking out a window. If you've built a hardware cockpit, you'll find yourself moving your head to look around things.

Once the image is far away, you no longer have binocular cues to tell you what is near and far; other cues take over, primarily perspective and contrast. Without the binocular cues screaming "MONITOR THREE FEET AWAY!", your brain can pay attention to the other cues, and the image actually feels 3-D.

In addition to the feel of the distant image, the seamless wraparound filling your peripheral vision adds alot - you really feel like you're moving, even though you're sitting completely still. I've piloted demo flights for several people; one had to quit because she started getting motion-sick, and two almost fell out of their seat.


EDIT to capture your post made while I was typing:
X-Plane doesn't do multiple visual windows on a single computer. To get past ~120, you'll need multiple computers.

[Salire]

Thanks Wayne. Yes, I think I'm sold. I think the Citation sim I had a chance to fly years ago at AA training center near DFW had a WAC type display and I was bowled over.

I haven't tried this yet, but I *think* I could use a TH2GO with X-plane and stretch the horizontal FOV out to 180. I've tried this with an aux monitor on my iMac i7 and set it to 120, and it worked fine. As long as the computer can keep up I would think it would work without having to go to a multiple pc config (and the ridiculous commercial X-plane license). I'm probably going to build a PC to run the sim/visuals, so I'm not totally wedded to X-plane, but that's where I'm starting.

S

[wledzian]

X-plane doesn't do 180°. It's not a matter of stretching.

Like just about every other graphics engine out there, the visuals in X-Plane are generated with a perspective frustum - picture a pyramid drawn as lines from your eyes to an imaginary rectangle in front of you. To go wider you make the rectangle bigger and/or move it closer to the eyepoint. No matter how big/close it gets, you cannot achieve 180°. Also, as you approach this limit, the detail becomes very compressed towards the center and the edges get very stretched. Anything beyond ~120° becomes nearly unusable.

We get around this limit in FSX by using multiple windows. Gene and I are using three windows of ~80° each, to allow for overlap and field loss due to the warping. As X-plane does not support the use of multiple windows, you're limited to what is reasonable to produce in a single window

While the X-Plane manual implies that extreme wide views are possible (cylindrical / spherical projection modes), these are post-render effects which simply warp the perspective frustum after the fact. Due to the distortion required, the edges of the image in these modes are fairly sharp, but the center gets very blurry, especially at wide zooms, and is still not capable of achieving or exceeding 180°.

[Salire]

Ah, ok. The pyramid illustration made it clear. Thanks. This would explain why trying ~120° on 2 monitors seemed pretty good as a test. Would you say that ~80° is close to the limit you'd go for each?

[wledzian]

For our display, that's about as wide as we'd go. When you're dealing with front-projected screens, there comes a point where the curvature of the screen starts to limit the width you can use. If you're using a rear-projected screen, however, you don't have such limitations. If you can project to it in focus, you're good to go.

[Salire]

Did you build basically to the limit of the available mylar width to still give you 40° vertical?
In thinking of the variables one has to consider, I was wondering what the relationships are between distances between viewers, screen, and mirror and how they affect, for lack of a proper term, an acceptable viewing zone (perhaps also an oblate spheroid). From your ray drawings, I understand that the screen/mirror distance is determined by ray convergence and the specific shape of the oblate spheroid of the screen are driven by the viewer offset. I suppose then that the acceptable viewing zone would be a function of the mirror radius and the degree of viewer offset from the axis?

BTW, what software did you use for the ray diagrams?

[wledzian]

you are largely correct in your understanding of screen geometry generation. our design basically assumed a single viewer at the display axis, offset a bit because your eyes are in front of your neck. Due to the way the ideal screen shape changes with offset, a real multi-viewer cross-cockpit display cannot be fully collimated at all points. The screen shape will be determined by a surface which will appear distant to both viewers, but will not be behind the ideal surface for either viewer. So long as the image forms at a sufficient distance to negate stereopsis, it will work.

Regarding our design size, it was a grand confluence of coincidence. I had a design worked out for 15° up, 25° down with a 48" radius, but Gene had already begun cutting parts for +/- 20°, also at 48" radius. I did the raytrace and determined that it would work, albeit with a bit of crop at the top from the bottom screen edge. We decided that this would be acceptable, as it would allow the additional immersion of leaning forward and looking up at otherwise-hidden sky. 40° vertical was chosen as the largest vertical FOV that we could get with a centrally-located pilot, mainly due to the ~2% maximum stretch of mylar at the peak of the stress/strain curve. Pull more than that, and the mirror deforms uncontrollably and pops like an overinflated bubblegum bubble. 210° horizontal was just going to 180° by design, with about 15° usable in each 'ear'. It also happened to coincidentally be exactly the limit of what we could get out of the 56" mylar that was available.

The software for the ray diagrams is a spreadsheet in Excel, entirely of my own creation. At some point, I may convert it to a stand-alone app coded in VB.Net, but I'm not planning to release the Excel version.

[Salire]

Having done this, what would you do differently in the next implementation? What would you say is the optimal vertical FOV centerpoint? I can see the benefit of having more sky visible for effect (when leaning forward), but is it worth it to restrict the view of the ground when looking out the side window?

How large would you say is the zone where you get an acceptable image? Are there disorienting effects by moving your head? Is it more sensitive to distortion in one axis? I'm guessing it would be most sensitive to vertical head movement.

Thanks,

Sal

[Salire]

I put together a spreadsheet and played with various configurations. It seems that for a couple of reasons, the ±20º FOV worked well for you. I had a lot of trouble arranging a cockpit to work with the 15/25 and 20/20 is more in line with FAA cockpit design guidelines (see FAA AC25.773-1), at least for transport category airplanes.

I understand your mylar stretch constraint, but this appears, at least in the 48" radius design, to have limited your effective vertical viewing area of the mylar to be about 36" of the width (at a 40º FOV). It's a shame that you can't use more. Don't you have about 48" or so available after accounting for a margin to tape the mylar to your 'goggles'? I haven't worked out the geometry yet, but perhaps you can use more of the mylar as the radius increases?

Another issue I had and thinking about the 48" radius was that the proximity of the mirror comes into to conflict with placement of an instrument panel/glare shield if you use a typical eye to instrument panel distance of ~30".

S

6146

[wledzian]

You are correct - the bottom edge of the mirror does start to intrude on the panel structure if you want the panel that far out. The entire design becomes an exercise in compromise.

When the mylar is fitted to the frame, it is initially in a conic shape. This conic shape unrolled requires more mylar width than the mirror chord length might indicate. You can go bigger if you limit your horizontal FOV, but for the configuration we've used, the design requires a full 56" width.

[trevj]

Hey guys, I am happy to have found this thread via google - some great info here and some great work. One thing I am curious about regarding the rear projection screen: has anyone tried the vacuum method for creating the screen as well? I'm thinking a latex sheet for the membrane, and a glass panel for the back surface could give nice results.

I also wonder also if using some type of cloth which is impregnated with clothing starch in conjunction to the latex membrane might yield a cloth screen that would retain the correct shape when dried even without a vacuum. This might get tricky, although I am betting a similar technique would work really well for creating a front projection solution if you used layers of plaster impregnated cloth and formed it over the membrane. If this has been talked about already, I'm sorry, I haven't gotten through the entire thread yet. :D

[ts11iskra]

Wayne and Gene,

Like everyone else I'm overly impressed with your accomplishments; simply amazing. Like many others, I too want to build a collimated display for my simulator.

I've quickly reviewed your postings and looked at your videos online but there's a lot to take in. I'd like to reach out to you via email if acceptable?

For the sake of the thread, I am wondering if there is a better method for applying and then holding the vacuum? One of the thoughts I had was to wrap the back of the Mylar mirror structure (the wood and particle board) in Boating Shrink Wrap. I've been watching a few videos and it would seem to me that the material would make an excellent seal. If you wrap the entire mirror structure in this and create a seal all the way around would it hold? The term they use when wrapping boats is to "weld" the joints which can be done by overlapping joints, heating them and running your glove wrapped hand down the seam. Takes seconds. The shrink wrap should give it an excellent seal and professional looking finish. I see you use a shop vac and realize there is a lot of volume of air to remove from your structure but I'm wondering if the seal were 100% would a smaller vacuum pump with ample time do the trick? A simple vacuum gauge with an upper and lower limit switch could be used to maintain it. I had a vacuum pump years ago for automotive air-conditioning work and it was very quiet.

For that matter it might seems to me that the boat shrink wrap could be a good material for building the screen as it is white and will wrap tightly when heat shrunk. The only issues, the unknowns for me at this point is that all the samples I've found so far are glossy and I don't know how that would work or if it would create visual deformities but is still might make an excellent first layer. Perhaps it would take a coating of flat spray paint?

Well, I'm going to follow in the path you guys blazed here.

[geneb]

The idea has merit, but it may be overkill. :)

I learned in February that the way Wayne & I are doing the mirror is just about dead-on the same way the commercial guys are doing it. The UK simulator manufacturers tend toward a constant speed vacuum source and a bleed-air valve, very similar to the setup we built. (right down to how they detect the position of the mirror!) US firms tend towards a variable speed vacuum source. This is next on the experiment list. I'm hoping the variable speed system works well because based on my fiddling around with a speed controller, it's a LOT quieter than the bleed-air system. I'm hoping it's actually easier to tune the PID for it as well.

As to using the boat wrap for the screen - that might be a pretty interesting thing to experiment with. The only issue I can think of is that because it's heat-shrunk, it will follow every little shape defect in the screen.

Can samples of the material be had fairly cheaply? I've still got the original screen we built for the prototype and it would be interesting to see how it looks on that.

I wouldn't worry about the glossy-ness of the material though. You go over it with some 000 steel wool to roughen the surface, clean it carefully and then shoot it with whatever paint you'd like.

g.

[arnolde]

Hi Guys,

Just imagine, if you could had a supplier for bigger Mylar sheets, what size would you need/want if you wanted to build another, bigger mirror?

regards,
E.

[wledzian]

We have found a supplier. How big are you imagining?

[arnolde]

upto 12 feet wide

[wledzian]

for a 12 foot wide mirror (6 foot radius), you'd need about 24 feet of 82" mylar.

[arnolde]

so does that mean, the largest piece of Mylar you'd ever want is 7x24 feet?

[wledzian]

No - a 6-foot radius mirror would barely accommodate a C172-sized cockpit. If you want to put a collimated display around an airliner cockpit, you're probably looking at ~9 foot radius minimum, or ~36 feet of 120" mylar.

[arnolde]

Which gets very close to a commercial mirror size... and price ;-)
Well anyway... if anyone here wants wide Mylar (4-12 feet wide, 20-50 feet long) then feel free to ask me.

[Salire]

A 6' radius is the sweet spot for my project. I'm glad you guys are focusing on this. I'm also interested in the options for vacuums. I'd thought of the variable speed and am interested in your results. From my reading, I'm under the impression that very little vacuum pressure is actually required. Have you thought about things like bilge blowers?

[Salire]

Or maybe a kitchen ventilation blower?

[super2277]

Hi!

how much is needed for half circle curved screen for 737ng with shell :)? wide and lendght

[wledzian]

See post #299
http://www.mycockpit.org/forums/showthread.php/21310-Question-about-collimated-display-systems?p=132173&viewfull=1#post132173

[Dinther]

This is the most fascinating thread I ever read. Very exited about the results achieved by wledzian and geneb also surprised why it has gone so quiet around your efforts.

Anyway, to give your results some reproducible backing. For that I want to produce a Sketchup model with mathematically correct dimensions. The reason I use Sketchup is because I have a copy of Shaderlight 2 which enables me to do raytracing and thus virtually experiment with variations to your setup.

I like to see a much more accurate description of what exactly the guideline dimensions are. You speak of a spherical section meaning a piece of a perfect hemisphere. If so, which piece? Can you define the upper and lower part of it in degrees?

Same question with regard to the projection surface. I believe you said both hemispheres have their center at the same point. Is this correct or was there some tweaking. After all, the viewers eye position must be important here too.

What exactly is the viewers eye position anyway?

At the start of the thread people correctly speak of a parabolic mirror. A parabola is not spherical. The characteristic of a parabolic mirror is collimation, a spherical section does not do that. Interestingly when a chain is suspended between two points it naturally forms a parabola. The same is true for a piece of mylar under vacuum I suppose.

Would it be right to conclude that your mirror is spherical in a horizontal axis and parabolic vertically?

7282
Image of sketchup model. The model uses a parabolic mirror. (Not a spherical section because I simply could not get that to work)

7281
Image of shaderlight 2 raytrace. In this raytrace you can see how the office environment is reflected in the mirror and also a piece of the screen with test pattern. Obviously things should fall in line when the viepoint moves to where the pilot would sit. I have not achieved this yet as I don't have any real solid data to model with. I hope those details will be made available so that we can have a solid record in once place how this screen is done right.

Sketchup model can be downloaded here: Collimated display study by dinther - 3D Warehouse (http://sketchup.google.com/3dwarehouse/details?mid=bb5652ad511ffad81a5808183c880760)

[Mike.Powell]

The mirror surface in a commercial collimated display system is spherical, not parabolic. With the appropriate frame, a mylar sheet stretched by differential pressure will form a very nearly spherical surface. The shape of a hanging chain is a response to the unidirectional gravity field, while the mylar shape is the response to non-unidirectional pressure which is normal to the curved mylar surface.

Spherical optics introduces geometric image distortion. This is compensated by warping the image source. To a first approximation the image is placed on a spherical surface having a radius half that of the mirror and sharing the center of curvature. Further optimization moves the image surface closer to the mirror with the result that the image surface is technically a toroid.

Google's US patent search is a good source of information on this technology. Search on "infinity displays".

[Joe Lavery]

Hey Mike, you lost me at Commercial.. ;) I think I have the skill to build one of these and the tools to do it, but I'd need at idiot's guide to the technical side of things.

You should write a book on the construction, with plans and dimensions I'm sure there's a sale for it.

Joe.

[Mike.Powell]

Hey Mike, you lost me at Commercial.. ;) I think I have the skill to build one of these and the tools to do it, but I'd need at idiot's guide to the technical side of things.

You should write a book on the construction, with plans and dimensions I'm sure there's a sale for it.

Joe.

I think Gene is working on that though I don't know what the status is.

[wledzian]

I've been handling the optics design, and Gene has been taking it from there, designing the structure. We still can't sell full kits or plans, as one critical element is still under active patent. We can get you pretty close, and there's enough information available here for you to take it the rest of the way.

Dinther, the mirror is spherical, not paraboloid. True, the collimation is not perfect, but it doesn't have to be. It just has to place the image far enough away that stereopsis is no longer the dominant depth cue. Motion parallax and perspective take it from there. Trust me when I say the effect is stunning.

[castle]

I think Gene is working on that though I don't know what the status is.

yes, Gene is just about done with the design for a 737 setup so i won't steal his thunder.;-)

But a couple of things to keep in mind.
1) you will need a large space around the cockpit. it is a large structure. The projection screen alone has a radius greater than 5 feet and the mirror structure has a diameter over 16 feet and you will need some room behind the structure for walk-around space. having a 12 foot ceiling helps. you might get by with 10 feet. I will be building mine in a 14x24x12.5 foot garage stall.


2) a CNC router is almost mandatory. precision is a must and the projection screen has 63 ribs forming the surface.

3) would recommend a mylar width of 116 inches. The design calls for a minimum of 107" with margin of 3" on each edge. It is a huge piece over 30 feet in length; coming up a little short in gluing the mylar to the frame is a no-no, you can trim the excess, but you can't add a patch segment.

Wayne and Gene have done a fabulous job and will share the design sans the patent with anyone crazy enough to accept the challenge. But it can be worked out by studying the patent, crunching the numbers and observing and viewing the pics.

Gene will be writing a "howto" doc on the design and instructions for building and I will also be adding my two cents along the way.

Jack

[wledzian]

Dinther - give me a day or so, I'll upload the mirror-screen geometry to 3D warehouse. You can try the actual design geometry with Shaderlight to see that it works. Note that the screen is not located at R/2. The screen shape is very important in properly placing the image - as little as .25" out of place will put the image either too close to appear collimated, or beyond infinity, causing diverging focus, which is very hard on the eyes.

EDIT:
Model containing only the mirror, screen and default cardboard-cutout girl has been uploaded to 3D Warehouse.
Collimated Display Optics by wledzian - 3D Warehouse (http://sketchup.google.com/3dwarehouse/details?mid=1e0b5ecac8d7a9a1414711d97d662467)

[geneb]

The design review is done and after a few adjustments are done, poor castle will be up to his neck in trouble. :)

The assembly manual will be written once I've got a chance to tweak the single-seat design that Wayne & I built.
I want to incorporate the changes from the 737 part design into the smaller one. This will "normalize" the components across all three designs so one manual will work for all three.

Castle is correct - CNC cut parts are pretty much a requirement. You'll also need a full size (not a table-top) band saw in order to post process some of the parts.

g.

[super2277]

well i have a small room and i wondering if its even posible to have the colimated dispaly in my room? i almost dont have enough space for the cockpit shell but the colimated dispaly they are using in real cockpits that stands on hydrolics where pilots training, will that colimated display work?

[castle]

well i have a small room and i wondering if its even posible to have the colimated dispaly in my room? i almost dont have enough space for the cockpit shell but the colimated dispaly they are using in real cockpits that stands on hydrolics where pilots training, will that colimated display work?

Probably not, those have a larger radius mirror of 9 feet plus where as Gene and Wayne's design is 8 feet whch is just about the minimum radius for the 737. For a full 180 degree mirror the diameter at the end points is 16 feet plus about another foot for the top of the frame. The projection screen has a radius just over 5 feet and you need to have a ceiling height over 10 feet. It's a large structure.

JW

[OmniAtlas]

Have you guys thought of integrating Paul Bourke work (iDome) iDome images (http://paulbourke.net/dome/iDome/) with mylar material?

BenQ has just launched an affordable 1080p short-throw projector (~1000 USD, W1080ST model) and it may be possible to do wrap around visuals with one projector. This is the route I'm looking into, to obviously try and save cost.

[castle]

[QUOTE=OmniAtlas;137759]Have you guys thought of integrating Paul Bourke work (iDome) iDome images (http://paulbourke.net/dome/iDome/) with mylar material?

BenQ has just launched an affordable 1080p short-throw projector (~1000 USD, W1080ST model) and it may be possible to do wrap around visuals with one projector. This is the route I'm looking into, to obviously try and save cost.[/QUOTE

Dome projection systems do not create a virtual image as do collimated mirror systems. And there are significant differences in how the image(s) are created and the effective FOVs.

[super2277]

how much does the colimated display take? for a 737 without the shell, just the interior

[jthiani]

This has been a very informative thread. Not sure if it was posted or not but who supplies the mylar in sheets wider than 55" ?? Im having a devil of a time location anything wider online .... Thanks in advance

[cotheseest]

That might help, but I confess to being a little confused about what the real difference in an "article", "blog" and quality "forum" post is...For the photo threads perhaps consider some sort of form with pistol information? Way to make a picture a required element?

[Tesla3D]

http://i.ebayimg.com/images/g/y-8AAOSwyWZZSBsL/s-l500.jpg
Search ebay for http://www.ebay.com/itm/12-set-Arcade-Tesla-II-Cockpit-Simulators-Collimator-Mirror-Beam-Splitter-C20-/282529151787

This would only be good for a single pilot. With 2 a side-by-side pilots. See the image of the glass mountain (Flight Safety International) Concave mirror and beamsplitter.
The 20" flat screen monitor is on top facing down. So, the footprint of the optics is vertical. The doors slide for complete isolation.
The cockpit controls could be replaced. But, this is about the smallest footprint 3.5' wide, 7'long, 6.75' high to get a VR.
At least it can provide the mental model.
An updated 1080 or 4K monitor should do well if the refresh rate is high to preserve true color.

[OmniAtlas]

http://i.ebayimg.com/images/g/y-8AAOSwyWZZSBsL/s-l500.jpg
Search ebay for http://www.ebay.com/itm/12-set-Arcade-Tesla-II-Cockpit-Simulators-Collimator-Mirror-Beam-Splitter-C20-/282529151787

This would only be good for a single pilot. With 2 a side-by-side pilots. See the image of the glass mountain (Flight Safety International) Concave mirror and beamsplitter.
The 20" flat screen monitor is on top facing down. So, the footprint of the optics is vertical. The doors slide for complete isolation.
The cockpit controls could be replaced. But, this is about the smallest footprint 3.5' wide, 7'long, 6.75' high to get a VR.
At least it can provide the mental model.
An updated 1080 or 4K monitor should do well if the refresh rate is high to preserve true color.

C-20 Glass Optics device....http://www.mycockpit.org/forums/showthread.php?t=30397

[cotheseest]

We have a Lowrance HDS-12 Gen2 Touch display unit that is ready for a new home.1200.00 Also did you know that there are vin reports cheaper than Carfax? Try this website https://vindecoder.biz

[Horgy]

Here I am, 8 years after the creation of this original thread.... Did much come of it?

I've seen Youtube videos from F15Sim of a collimated display created, and it's very impressive. I have a real shell and I'm thinking about potentially trying to create a collimated display for it. Do people still follow here? Has much changed? I scanned through and other than patent references there isn't much information I could glean on how to calculate the mirror size of screen size - albeit I found some of the material confusing.

Can anyone bring me up to speed? How should I go about calculating the mirror dimensions and screen dimensions, in laymans terms?

Horgy

[remcosol]

Hello Horgy,

I still have a complete mirror (2 piece) laying around from a dc-10 simulator . If you are interested and live in europe let me know!
Remco

[castle]

Here I am, 8 years after the creation of this original thread.... Did much come of it?

I've seen Youtube videos from F15Sim of a collimated display created, and it's very impressive. I have a real shell and I'm thinking about potentially trying to create a collimated display for it. Do people still follow here? Has much changed? I scanned through and other than patent references there isn't much information I could glean on how to calculate the mirror size of screen size - albeit I found some of the material confusing.

Can anyone bring me up to speed? How should I go about calculating the mirror dimensions and screen dimensions, in laymans terms?

Horgy

Browse over to the "2 Place Collimated Display" thread for more info, pics, and videos

castle

[geneb]

The largest issue you're going to have is getting the Mylar needed for the mirror cell. Packaging Industries was the only place I knew of and I'm not sure they're still in business.

g.

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