Question about collimated display systems.

[Babeloe]

How about one of these space blankets? If you don't know them see http://en.wikipedia.org/wiki/Space_blanket.

I don't know if they are actually made of mylar, but they are often called 'mylar blankets'. And they are pretty cheap, and you can get them in a lot of outdoor stores and on the internet.

The downsides I can see is that they are folded very tightly because you need to be able to put it in your First Aid kit, so they will have some pretty sharp folds of witch I don't know if you can get them out with the vacuum or any other way. And it might be a problem with the size, but I think they should be big enough to cover a person's body so a small display should work.

I don't know if it works, but is nearly too cheap to not try this. You can buy these blankets for about 4 euros I think.

Just an Idea

Babeloe

[Babeloe]

How about one of these 'space blankets' they're made of mylar and pretty cheap. http://en.wikipedia.org/wiki/Space_blanket The only downside i see is that they are folded.

[SU-Medo]

Hi Hessel ..

It's "Mohammed" you can call me Medo if you like

I appreciate for you your reply .. Thank you so much !
The wikipedia link about "Polyethylene terephtalate" that you provided me is so useful , I don't like just following steps without knowledge , I like to understand everything about what i plan to do ..

Thanks Hessel

[riche543]

ricardos link worked for me here in oz.
Great vid but she makes it sound so simple..lol
Cheers..

[Atomic_Sheep]

Sorry to butt in with noobish questions but I've got 2:

1.)

Metalized Mylar can be used to make film collimating mirrors. Up to about 40 degrees of vertical field of view, building one is merely difficult. Building one with a 60 degree vertical field of view apparently requires magic. SEOS figured it out a few years ago. Rockwell Collins was so impressed they acquired SEOS in 2008.

What makes 60 degrees so much harder than 40 degrees?

2.) lets talk resolutions or maybe more appropriately aspect ratios? But I haven't really started thinking about the displays of my simulator yet so I don't quite know how to talk about in a way other than layman terms. So, lets take 800x600 resolution and let's take the 40 degree by 60 degree 48" section that geneb has taken for his display. First, how can you display a square image on something that isn't of the same circumference at the top and bottom? Second, the 40 degree (height? wise) and 60 degree (horizontally? wise) gives us a viewing area of approximately 3:2 ratio? The closest one that I see to this would be 16:10 i.e. something like 1280x800 so essentially widescreen? As I said, I don't quite know how displays work so I could be totally wrong in what I'm saying but I hope I've but my question across with enough clarity.

EDIT: Just some additional information, when I tired the SAAB and Airbus simulators, I distinctly remember distortions in the image but they were generally down the bottom and off to the sides. You had to strain/be stand upish to see them so professional displays aren't as perfect as you guys might think (for those who haven't been in the real thing that is). In fact, when you find out the price, you're almost disappointed!

[Mike.Powell]

The Mylar initially is a flat sheet and must be stretched into a spherical-section shape. Beyond about 40 degrees vertical arc the stretching exceeds the plastic range of the Mylar. Because its properties change, it's more difficult to make the sheet form a spherical-section surface of a quality suitable needed for the application.

When projecting onto a spherical-section surface there will be geometical distortion. It's compensated for using image warping software like Nthusim.

Agreed, collimated displays are not perfect. The designs tradeoff collimation effectiveness, view box size, distortion, and so on.

[geneb]

All commercially produced collimated displays have a distortion band around the perimeter edges of the mirror. Those bands are typically masked by physical structure. That's why the only way you'll ever see them is if you move your head to see over/around those masking elements. The only time you'd ever do that is if you're doing it on purpose, which is your own fault at that point.

The 60x40 mirror was a proof of concept device. I was using an 800x600 projector because that's all I had available. The full system we're working on now will cover 190 degrees of "intentional" mirror, and out to about 225 when you include the "ears". The video will be provided by three Epson 705HD projectors that run at 1280x800 (and thanks to the kindness of Matt O., I'll be able to run them at that res instead of 1280x768 due to the limitations of the analog TH2G.)

Constructing a 60 degree vertical FOV mirror is mechanically tricky I suspect. Note that the current FAA Level D certification requirement is only 36 degrees.

g.

[castle]

The Mylar initially is a flat sheet and must be stretched into a spherical-section shape. Beyond about 40 degrees vertical arc the stretching exceeds the plastic range of the Mylar. Because its properties change, it's more difficult to make the sheet form a spherical-section surface of a quality suitable needed for the application.

When projecting onto a spherical-section surface there will be geometical distortion. It's compensated for using image warping software like Nthusim.

Agreed, collimated displays are not perfect. The designs tradeoff collimation effectiveness, view box size, distortion, and so on.

Just wondering, can you apply a little "slack" when installing the mylar; you know the radius of the desired shape, compute the arc distance say for 40 degrees at 6 feet requires (40/57.29) * 6.0 = ~4.188 linear feet of mylar in the vertical when the mirrot is formed. The chord distance between the upper and lower frame is something less, but say the mylar is attached with a 4 foot width, will it stretch uniformily to form the mirror, and if that is the case would reducing the amount that the mylar has to stretch allow for a greater vertical FOV.

JW

[Mike.Powell]

Just wondering, can you apply a little "slack" when installing the mylar; you know the radius of the desired shape, compute the arc distance say for 40 degrees at 6 feet requires (40/57.29) * 6.0 = ~4.188 linear feet of mylar in the vertical when the mirrot is formed. The chord distance between the upper and lower frame is something less, but say the mylar is attached with a 4 foot width, will it stretch uniformily to form the mirror, and if that is the case would reducing the amount that the mylar has to stretch allow for a greater vertical FOV.

JW

I don't know, but I'm inclined to think doing so would introduce unacceptable distortions.

When flat, the Mylar does not have straight sides. The full sheet is actually a broad arc. If slack is added, the edge dimensions must change somehow. Somewhere you'll end up with extra material and wrinkles when fastening the Mylar to the frame.

Build a scale model and experiment with poly drop cloths.

[737NUT]

Anyone tried Chrome monocote? When heated it becomes drum tight and is fairly strong. Also can be attached to itself to make bigger sheets.