Brainstorming for a collimated mirror display

[Matt Olieman]

Mike, thanks for that wonderful explanation, as always a true engineer using proper terminology

Twizzstyle (using that for lack of know your name), you show the projected image (above the cockpit being flat) as Mike mentioned it should be spherical.

Wouldn't it be wonderful for us to be able to build one of these and have the technology to do this at a reasonable cost

[Twizzstyle]

Mike, thanks for that wonderful explanation, as always a true engineer using proper terminology

Twizzstyle (using that for lack of know your name), you show the projected image (above the cockpit being flat) as Mike mentioned it should be spherical.

Wouldn't it be wonderful for us to be able to build one of these and have the technology to do this at a reasonable cost

My name is Sean But either name works, haha

And yes, I do plan on having the image screen spherical. It is much easier in my code to have it be flat for the time being until I figure out exactly how I need to do this. Then I will probably write a new code that is a little more precise with the curved image screen. And again, my screen (well... the mirror) is still just going to be a forward view, as my flight deck is built into a closet. But this same principle could be used for a full width mirror as well.

[Trevor Hale]

My name is Sean But either name works, haha

And yes, I do plan on having the image screen spherical. It is much easier in my code to have it be flat for the time being until I figure out exactly how I need to do this. Then I will probably write a new code that is a little more precise with the curved image screen. And again, my screen (well... the mirror) is still just going to be a forward view, as my flight deck is built into a closet. But this same principle could be used for a full width mirror as well.

Please excuse my ignorance here Sean, but I am trying to understand how you can take the information from the computer and make the screen itself. What i am getting at, and hope you can help me understand is... if the computer program can build the shape of the screen, would you in essence get that program to give you the measurements of the screen itself? The computer program is flawless but won't account for the human error factor, or building material flaws, Do you think these problems can be overcome?

Thanks,

Trev

[Twizzstyle]

That's why I have reservations about this. Something like this needs to be VERY precise, and thats why the real thing is so rediculously costly. Still a fun engineering excercise to try to do it frugally anyways And thats what the whole flight deck is all about!

So yes, you had it right. From the code I'll be able to get profile curves that I can use to make a frame of sorts. Imagine a grid of plywood or MDF sheets that each have the profile contour. Then I will sheet that with some kind of flexible material (I was thinking some thin ABS or plexiglass, something I can heat up and form into the frame) and then the mirror film over that (assuming the mirror film can be shaped enough).

Please excuse my ignorance here Sean, but I am trying to understand how you can take the information from the computer and make the screen itself. What i am getting at, and hope you can help me understand is... if the computer program can build the shape of the screen, would you in essence get that program to give you the measurements of the screen itself? The computer program is flawless but won't account for the human error factor, or building material flaws, Do you think these problems can be overcome?

Thanks,

Trev

[Trevor Hale]

Ahhh, so it is indeed a complex project then. Ah well, Either way you will have one heck of a nice screen in the end to paint White and project your image directly on it. LOL

Please keep us posted.

[Twizzstyle]

Ahhh, so it is indeed a complex project then. Ah well, Either way you will have one heck of a nice screen in the end to paint White and project your image directly on it. LOL

Please keep us posted.

haha! Exactly!

[Mike.Powell]

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?

The collimating mirrors used in sim display systems are typically spherical because that shape is easiest to make. To reduce the overall weight, the mirrors are often made with aluminized mylar fastened to a carefully shaped frame such that there is a sealed volume behind the mylar. A small vacuum in the volume causes the mylar to stretch into a concave spherical-section shape. I suppose technically it's a 2-D catenary, but by choosing the proper shape for the frame, the mylar closely approximates a spherical section. There have been systems utilizing "hard mirrors" made of glass or of metal which could have been formed into a parabolic shape, but I've never run across one.

Spherical optical elements (both mirrors and lenses) do not have true focal points. However, for optical paths that are both close to and nearly parallel to the center path through the optics, it's a good approximation to say they do. We can extend this approximation to a flat surface intersecting the optical axis at right angles at the focal point. This is the so called focal plane. As long as the optical paths are close to the optical axis we can form images of reasonable quality on (or from) the focal plane.

Large optical systems like panoramic collimated displays wildly bust this approximation. In these systems it doesn't make sense to refer to a focal plane or focal point because you can't form a reasonable image using a large flat source image. You can, however, form a very nice image if your focal surface is curved rather than planar. For a spherical collimating mirror of radius R, the focal surface is a spherical section of radius R/2 that shares the mirror center of curvature.


Companies like Glass Mountain Optics and SEOS, makers of sim display systems, used to have web sites with more technical information. Now they're simply marketing contact points. Currently, the best source of information seems to be the Patent office. You can search patents for free using the Google patent search. Use terms like "infinity display", "collimating mirror" and "film mirror". The down side of reading patents is that the state of the art has improved a lot. Older patents show designs that are overly complex. Current panoramic display systems have one big mirror and one big screen. Wading through a bunch of old patents may be confusing at first, but it will introduce you to the technology.

While the display system company web sites don't provide much detailed information, some at least do provide product pictures that give a feel for the general optical system layout.

[Matt Olieman]

Trevor, also keep in mind, the slightest dimple on the mirror can make the image way out of wack.

I believe the spherical mirror backing is formed on a die. The form has thousands of tiny (micro) holes. Glue is applied to the form and the mylar film is vacuumed to the form.

Not much room for error here

[Mike.Powell]

Another reason for using spherical mirrors is that the crew will experience the same mirror curvature regardless of their position. If it were not spherical, different cabin positions would perceive differing image distortions. The symmetry of a spherical mirror leads to better image quality throughout the cabin.

[Matt Olieman]

I can only drool and fantasize