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jeff122670

Heads Up Display

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Yeah, those are.. but the type you would want to use are flat fresnel lenses, with a low magnification factor. In addition, you would need an air coupled Petzval lens for focus or zoom adjustment..

 

aaah.. you are making me remember stuff from my intro to optics "fluff" class i took in college.

 

You know... I have two EXCELLENT schools near me with world class optics labs in them. I'll see if I can pull some strings and get some time in front of a graduate student or professor to see how to do this best. If its that feasable.. something like this could possibly be brought to market for the GA community, or open sourced. hmmm

 

Time to pay a visit to RIT or U of R optics labs... I don't ahve anything else to do tomorrow. heh.

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Heh,

cold winters in New England make me bored...at least until i get the garage indulation done do I can work on the Cozy...

 

That website has an interesting pdf on their lenses and talks about different applications.

http://www.fresneltech.com/pdf/FresnelLenses.pdf

 

If I'm understanding (and it's unlikely that I am :confused: ) the flat lens fresnel acting as a collimator would have the image display (LCD or whatever) at the focal point? then the collimated image is what gets bounces on the reflector?

 

Where in the path would the Petzval lens go? I'm guessing between the fresnel and reflector?

 

Ooh, somethign else I just thought of....Optimally would you want the smallest, brightest and highest resolution screen you could get?

 

Ugh, need more beer..

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I can ask all those questions tomorrow to an optics person at one of the schools around here.

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check out:

 

www.anchoroptics.com

 

i have bought most of my beamsplitters from them!!

 

more tomorrow..

 

goodnight!

 

Jeff

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Oh wow.. looks like someone has already done it. We can do something materially similar, I think.

 

And yes... Anchor optics is awesome. :)

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re:

 

"How would you handle focusing the display at infinity? That's how

military HUDs are setup. This lets you see the image without having to

refocus your eyes. I'm not sure what the optics involved would be but if

they aren't cost prohibitive for mere mortals it might be something worth

considering."

 

*********

 

Possibly a segment of a blown Plexiglass bubble could be used as a combination beam splitter and lens.

 

Have to think about what shapes a bubble will naturally assume, i.e. blown upward vs downward.

 

This process will never form a perfect lens, but may just be "good enough" !

 

**********

 

The "red dot" rifle/pistol scopes use a convex/concave lens, using the concave surface facing the user to reflect a dot from a small LED,at the user and focused at infinity.

 

The optical path through the lens looking at the target has zero magnification.

 

Hence the convex and concave surfaces are parallel, with a uniform thickness over the entire lens.

 

**********

 

Can one go one step further and reflect an image off of the canopy ?

This may be just asking a little too much !

 

JCP

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You could reflect an image off the canopy (using it as the secondary reflector/beamsplitter) but in order to do that, and still have a square image, your primary reflector would need to be optically matched to cancel the distortion that the canopy would cause.

 

If you are thinking of doing it like a car windshields, those are much closer to 'flat' than any Cozy/EZ/etc canopy I have ever personally seen, and therefore easier to correct for. The canopies in our aircraft would be a veritable optical nightmare. So are the ones in any F-xx fighter. That's why they project onto a nearly flat beamsplitter. Even those beamsplitters are not perfectly flat so they can correct for portal effect.

 

Portal effect: Your eyes are focusing through a single object to infinity, and therefore pointed slightly wider than they would be if you were focusing on something 3 feet away...

try this.. hold your index finger (or middle finger, if you are so inclined) at arms length. Focus out on some object in the distance... say.. more than 25 feet away. You will see 2 fingers. That's an oversimplication of the issue.. but represents some of the challenges that HUD display innovators face.

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Ahhhhhhh sooooooooo, two eyes complicates the problem !

 

Rifle/pistol red dot scope example is only a single eye.

 

Reflection I can see from inside surface on my right eyeglass lens is also only a single eye. (my left lens doesn't focus off of inside surface reflection)

 

Another one of my pipe dreams goes up in smoke !

 

Thanks for sharing your greater knowledge.

 

JCP

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Actually.. don't let your dream go up in smoke.. you CAN correct for it, a lot of the commercial models do.

 

Target          /-----     >oo (eyes)
                 |
   display  | ----/
All you need to do is curve the / piece of glass (the beamsplitter) along the vertical axis..

 

sorry about the atrocious line art. :irked:

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Do you realy need the extra 'turn'?

 

Target            /-----     >oo (eyes)
                     |
   display  | ----/


could you do this to simplify:
Target            /-----     >oo (eyes)
                     |
                     |
                 display

Bascially have the display pointed up.

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Do you realy need the extra 'turn'?

 

could you do this to simplify:

Target /----- >oo (eyes)

|

|

display

 

Bascially have the display pointed up.[/code]

Without the second mirror, the 'projected' display would be inverted and reversed. The inverted is easy to fix.. mount the display upside down. Reversed is a WHOLE other ball of wax, especially to process in real-time. Trust me, a second mirror is a much simpler solution.

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yeah, i think you have to reflect the image off the beamsplitter and NOT the canopy. that is how we do it in the F-15E and as you mentioned, it is done that way in any other fighter.

 

also, i think, to prevent even MORE lens issues, that you have to use the "two mirror" process to keep the image from inverting.....

 

here are the issues as i see them:

 

1. getting a piece of software that can deliver an EFIS that is worthy of a HUD (moutainscope, pcflightsystems, dynon) that you can run on a computer and brighten via an LCD display with a backlight.

 

2. brightening a display such as BMA, DYNON to allow for projection onto the beamsplitter

 

3. eliminating ghosting on the beamsplitter (two images). i think it can be done with antiglare...but i am not sure.

 

I like softare such as Vista or Grand Rapids that have a flightpath marker, but that may be asking for the moon...

 

i think this is doable it just need someone to do it...finally....

 

i love the pics that charlie posted...he used the dynon and it worked great...but i want to get rid of the brown and the blue for sky and earth..

 

Jeff

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Duh! Of course. I hadn't thought about the inverted and upside down issue. Thanks for the clarification.

 

I would like to see a unit that has it's own bright VGA LCD screen and takes any vga input. That way pretty much anything with a VGA out could be hooked to it. (Heads up Nintendo anyone? :rolleyes: )

 

Personally, I would like to have minimal data displayed on a HUD. Maybe attitude, velocity vector, airspeed, heading, altitude, etc...nothing as complex and colorfull as an full EFIS, just something minimal to reference. It could also act as an annunciator panel if hooked to an engine monitor or something smart like Al Wick's setup. If somethign isn't looking correct the HUD would flash the warning and then you could drop down to get the full picture...

 

I guess my biggest concern is making the HUD more prominent in my vision than what's outside..

 

Did that make any sense?

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You could reflect an image off the canopy (using it as the secondary reflector/beamsplitter) but in order to do that, and still have a square image, your primary reflector would need to be optically matched to cancel the distortion that the canopy would cause.

 

If you write your own system... Most graphics systems render the image into a flat viewing plane. You could, instead, render it onto a non-flat viewing surface, so that the image that is displayed on the LCD panel is distorted. If you get the distortion correct, the final image that the user sees reflected off the non-flat canopy will be square. Such techniques are used in good VR helmets, because they use one panel and a big lense to display both whats in front of your eyes and whats off to the side so that users have proper peripheral vision.

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^^ You are exactly right, however, you would not be using the total available pixels that particular display provides. I know that many LCD display & presentation projectors and what not have off center correction, called 'keystoning' if you get past the lenses optical keystone limit, the display starts to distort the image by dropping pixels along various axis. The result.. well.. isn't optimal.

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Software is lighter than optics!

 

If the art is kept simple enough, and monochrome, I don't think resolution will be terribly important.

 

OTOH, there would be no need for a calibration system, and the CPU would not need to be as powerful, meaning less power drawn, cheaper, etc.

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ok, let's corral the horses here.

 

we are not talking about writing software here.....the goal is to turn what is on the market into something different (HUD).

 

 

there are plenty of EFIS's and other systems out there that have been written and work without introducing additional testing and possible errors..

 

that is just TOOOOOOO "one-off"...

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I agree, K.I.S.S.

 

VGA display input, dual reflector setup... as they say.. wham, bam, thank you, m'aam.

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Yeah, not trying to be rude to emteeoh, but the optics and lens provide enough of a challenge.

 

we have the EFIS to do the job (which ever one we select)...the trick is to DISPLAY the image in HUD format and get a nice clear image...

 

i just thought of a way to possibly eliminate the brown and the blue. what if we overlayed a green colored "gel" infront of the EFIS. this is essentially a green filter (transparent green plastic) that is used to color spotlights, etc.. anyway, this would try the displayed image completely green.....not sure if that would work, but just an idea....of course that might just make a big green BLOG infront of the pilots eyes...

 

hmmmmmmmmmmmmmmmmmmmmm...............

 

Jeff

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Jeff, thats why I was suggesting the use of the EL display from Planar displays. They are available in any number of single colors, and accept a standard VGA signal... they just output one color..

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do you think those are a little cost prohibitive?? i really like the way they look, but the website doesnt say the dimensions, etc, etc..

 

what do you think?

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They are a bit steep. about a grand a pop... you order them to spec, sizewise...

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