My Collimated Screen Concept

[BradMick]

Howdy all! So, I started working on a more concrete version of my Sim Pit and as a 'what the ****' kind of study, decided to work up a collimated screen concept. I freely admit to borrowing ideas from both the sims I've seen in real life, the ones I've seen on the net, and the work done in this forum as well in the design of this. The idea is a small collimated screen to fit in my house. I have a total width to work with of 6 feet, maybe 6.5 feet total. The planned screen radius is 2ft 10in. The supports are planned to be 3/4in thick. The ring supports are planned to be 1/4in plywood, and the back is planned to be 1/8in backerboard. The biggest problem I'm running into with this right now is, I'm having trouble finding formulas for the ray tracing part. I can design it all day, but until I can actually see how the rays are going to bounce around on this thing, it's a bit of a pain. I'm looking to extend the thickness of the end caps to 4in to better match the height of the support rings which is 4in. All of this is being built in Lightwave (as you can see) with the intent of porting it over to an actual CAD program. My biggest question with this though...is this even viable? The building part of it i'm sure is the easy part of it...but with as small as this thing is, will it actually display the way its supposed to? The other thing I think I need to work out, is...right now it's designed so that the frames are flush with the support rings, which means when the vacuum kicks in, the mylar will be in contact with the frame ribs...i'm thinking of recessing that by an 1/8in. Anyway...will post more progress as I work out the design and get some feedback! Appreciate any and all input!

[BradMick]

Alrighty, so I spent another day refining the concept, drawing ray diagrams, and present now that work here. Hopefully I haven't jacked up the ray diagrams. I'd like for the folks that have more know how (I haven't messed with physics and optics for going on 13 years now...) to vet this for me. Attached is a significantly less nice looking version of the mirror frame but I've got the screen in there now. Looked like the optimum distance below the center of the screen radius point is 14 inches for this setup. Things I noted (unless I again messed up the diagrams with an incomplete and out dated understanding)...The optimum point to draw the screen seems to be right at half way point of the radius, which makes sense I suppose given that's the focal point for a spherical mirror. (focal point = 1/2 * radius). The FOV is +20 / -20 degrees, looks like it'll provide un-interrupted viewing based on seat position. To give a little bit more head room i'm planning on cutting out a portion of the bottom of the screen. Right now it gives roughly 8 inches of head room, which is fine enough given the size of this thing, a little more would be preferred though!

[BradMick]

Just finished up an updated ray diagram. Shifted the viewpoint forward 4" to center up the pilot with the screen. This resulted in the height of the screen growing by about 2" vertically. Any of the folks out there who know more about this than I please let me know where I've erred. It's been refresher physics tutorial videos via YouTube for the past few days, plus the awesome thread from here to get to this point.

[BradMick]

86 views and no replies? Ouch...Oh well, still plugging away. I did some more research and found out I was drawing my ray diagrams wrong, so I corrected that and then modeled up the basic frame of the main mirror assembly and then also did a render to test it out. It took a couple tries to figure out...but I threw a luminosity map of a panoramic park scene I found online on the screen to see how things would look. I'm pretty happy! I don't know if Lightwave uses the same type of ray tracing scheme that I used, but I feel this is a decent representation of what the screen would actually look like illuminated and working. going to continue working on the frame work. I have to figure out now how to simulate a projector so I can have that reflect off the mirrors and onto the screen and then reflected in the mirror. I think for a rough go, this works. Hopefully this'll generate some dialogue for improvements and thoughts! Also, there's a picture (it's dark and hard to see) that shows an outside view of the setup and the crazy screen effects when not located in the 'sweet spot' of the screen...now, the trick is to blueprint it, print it, and build it!

[fsaviator]

We're all just looking. I guess we're waiting to see the next step?
I am curious though as to what you plan to build/fly as a cockpit or setup. Your diagrams don't appear to allow much space for panels and controls. I'm not going to pretend to be an expert on this subject but from other projects I've seen, your mirror for a Cessna 182 is going to need to be at least 7.5 feet wide, while a 737 will be about 15 feet.
I've seen first hand how a mirror that was not wide enough threw of the view from an FO side to the point the sim was unflyable from there.

I am going to assume since you are tackling a project this size you have been tracking Gene and John's thread in this forum? If not, here it is: http://www.mycockpit.org/forums/collimated-display-discussions/24548-2-place-collimated-display.html

Good luck and I'm looking forward to your success.

Warren

[BradMick]

Thanks for the response! I just came back to the states after 5 years in Germany, was stationed in Illesheim. I did two flights into the Stuttgart International Airport too in my Longbow. Was awesome! Was flying parallel to an Airbus all the way to the south pad there!

The idea of this cockpit is a single seat, limited room cockpit. I primarily fly fighters and other single seat aircraft, or just fly by myself. Cross cockpit isn't a requirement for this design as it's going to be just me flying it by myself. I just don't have a lot of room for anything bigger than a single person cockpit unfortunately.

The 2 place display thread is awesome! I've pulled a lot of the inspiration for the design of mine from those threads. Reading and understand the issues involved has been a blast! I've definitely learned a lot in this process. Although...now that you mention it, I have to give a 2 place cross cockpit design a shot too...:)

[OmniAtlas]

Hey Brad, can you bring this to market? Collimated screens for the home user is still a very new concept...

The other route I'm going is to make a curve screen like the idome, or cobra -- Cobra Simulation - Cobra Curved Display Intro Movie (http://www.cobrasimulation.com/splash-intro)

[fsaviator]

Thanks for the response! I just came back to the states after 5 years in Germany, was stationed in Illesheim.
Illesheim... Stork Barracks or something... I can see the tie in with the Longbow. I used to be stationed in Nuernberg and Augsburg in the 90's. Love that area of Germany. I'm actually stationed in Stuttgart now. It's not Bayern (or Franken) but it'still better than anything else up north.

If you are looking at a one seater (or tandem) then I would guess it would work.

Good luck

Warren

[BradMick]

In so far as bringing to market...after reviewing the other threads I think I have to agree with the assessment of those gentlemen in that since pieces and parts are under active patent...probably not. I will post up as much of the work as I can as I go. I'll have to dig into the patent stuff and see where the legalities of all that stands. The 'ear' portion is the sticky part of the whole deal. Hopefully this'll work out well. I just gotta find a CNC shop here in good ol' LA (lower Alabama for the uninitiated) to cut the wood for me.

[geneb]

A good size for a single seat display is about 8ft in diameter. A Cessna 182 would require at least 14 feet in order to properly handle both the left & right seats.

BradMick, you might want to check out 100kGarages - Where projects are made by digital fabricators (fabbers) working with 2-D or 3-D digital fabrication tools (http://www.100kgarages.com) to see if you can locate a fabber near you.

Good luck!

g.

[BradMick]

Alrighty, so it's been a while since I last posted. In that time I've finally put together my own ray tracing worksheet. Right now it's not very user friendly, and it doesn't quite jive with what I've seen of wledzians work. I'm going to continue plugging away. Unfortunately all the free time I've enjoyed is about to evaporate as I'll be comin' off of leave and headed back to work. Hooray for Army Professional Development COurses! (not at all...). But, as I get more work done I'll post when I can.

Brad

P.s.

I'll work on getting the equations all put together so other folks can at least use them to work on their own stuff in a few days as well.

[tmcnam]

Hi Brad,
This may be a silly question but why are you not reflecting your rays off of the spherical surface representing the mirror? I'm pretty sure that is the only way to size and place the screen i.e take 2 or more parallel rays (like you have) and reflect them off of the spherical surface and where they intersect defines a point on the screen. I may be totally misreading your diagram so forgive me if I am. I am definitely not totally up on the optics but followed Mike Powell and wledzian's examples. BTW, where in Alabama are you?

Best Regards,
Tim

[BradMick]

After talking to wledzian, I think that I was working under a completely different set of equations and assumptions. For what I was doing, it's correct. You'll see the reflection the way you're supposed to for the purposes of drawing a mirror...but...it won't give you points of intersection other than passing through somewhere around the focus of the mirror. I'm not super well versed in optics either, so I'm learning this as I go.

In so far as where in Alabama, I'm livin' it up in beautiful and balmy Fort Rucker.

-Brad

[tmcnam]

I see, the lines intersect around the (non perfect) focus of the sphere. Your design looks really cool and I hope you finish it. There doesn't seem to be any one thing that is too difficult about building these types of displays but it all adds up to a pretty good project. Of course, that is only the case after Gene and WLedzian actually figured out how to do it.

I used to fly a Saab SF340 into Dothan back in the 80's when I flew for NorthWest Airlink and passed by Fort Rucker many thousand times. Balmy is definitely understating it.

Keep us posted on your progress...it's a very interesting thread.
Best regards,
Tim McNamara MD

[jthiani]

what ever happened to this project??