Brainstorming for a collimated mirror display

[Matt Olieman]

Hi Mike, Thanks for that wonderful information. As always your the man with all the knowledge, and always appreciated

I've got three rolls of 6' X 10' mylar, each having a different thickness. I've experimented and experimented and ...... well, you know how it goes

The collimated displays / infinity displays thing..... although that's the best, without the specialized tools and knowledge... it's almost impossible. But, I guess I/we can keep our hopes up, and someone will find a method for our madness

Keep feeding us Mike

[spitfire9]

Has anyone tried or would anyone have any info on the collimated displays they have for sale at Project Magenta??

I sent an email a couple of days ago asking about the cost but I haven't recieved a reply yet.
I have a feeling they will be quite expensive but would still be very interested to know if the visual display is that much better than some lcds in front of the windows????

[Twizzstyle]

Bringing back a bit of an old thread...

I've been really wanting to do this for a long time. I work in actual simulators from time to time, and the depth is just amazing, really adds a real feel to it (even in the non-motion sims). Currently my screen is about 6 feet from my eyes, and although its plenty big, it looks like its 6 feet in front of me... not off at infinity.

So my idea is to build a frame out of plywood, and then sheet it for the right contour. Then lay some kind of mylar material (if I can get it to stretch enough and form to the shape). I wrote a MatLab code to calculate the mirror shape...

[Matt Olieman]

I'm all for it!!!! If you can figure out how to make this, you'll be the flight-sim builders hero forever

[James Twomey]

That would be something if it could be figured out. Twizzstyle if I may ask, where in Washington are you located? Im located in Port Orchard.

[Twizzstyle]

I live in Kirkland, and work in Flight Test at Boeing (at Boeing Field)

I've confused myself a little on this though... the matlab code I wrote to calculate that shape just looks at geometry. When you look at the bottom of the mirror, it should reflect to the bottom of the screen (that is above my head), if you look at the top it should reflect to the top of the screen, etc. Just simple incident/reflected angles and geometry, and it creates that curve... But where I'm confused is on simple optics...

So aparently, in order for the image to appear behind the mirror (what we want here obviously) the object (the screen in this case) needs to be within the focal point of the mirror... mine is obviously way outside the focal point (the focal point is approx. half of the center of curvature)...

http://www.glenbrook.k12.il.us/gbssc...ln/u13l3d.html

So by simple geometry, my image should fill the whole mirror, but is it going to appear like it is right in front of my face?

[Matt Olieman]

The image or screen above the cockpit should also be curved to match the mirror (although smaller).

If I recall correctly, the bottom of the mirror actually looks at the top of screen rather then the bottom. So the image is projected upside down on the screen.

Please correct me if I'm wrong

[Twizzstyle]

The image or screen above the cockpit should also be curved to match the mirror (although smaller).

If I recall correctly, the bottom of the mirror actually looks at the top of screen rather then the bottom. So the image is projected upside down on the screen.

Please correct me if I'm wrong

Aha! Maybe that is the piece I'm missing that would fix my focal point location conundrum...

Should be very easy to just flip the direction that my code runs to do this... I'll see what it comes up with.

[Mike.Powell]

For a mirror collimated display, the image source is located on the focal surface of the mirror. The mirror is typically a spherical section. The focal point of a spherical mirror is located at half the radius. We're used to thinking of "focal planes" in optics, but this is an approximation that breaks down with the large optical angles needed in a simulator display system. Because of the large fields of view, spherical distortion becomes significant. To correct for this spherical aberation, the image surface should be a spherical section with a radius half that of the mirror. The mirror and the image surface will share the same center of curvature.

[Twizzstyle]

So here is what my code produced with the image screen flipped...



Mike - you say the image should be at the focal surface... now when you say focal surface, is this because there is no focal "point"? (because or the mirror curvature... maybe I should have my code find the focal point...) Then you go on to say the mirror is spherical, but this is not true is it? It is more parabolic?