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Heads Up Display


jeff122670

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They are a bit steep. about a grand a pop...

Yep, all of the 'daylight' displays are going to be pricey. It's a specialized market.

Bottom line, it is an area where you don't want to skimp, be it a HUD or touch screen type of interface.

For my glass panel project, I'm leaning more towards voice activated and audio feedback options.

The HUD would be nice for clearing off some panel space, if nothing else.

T Mann - Loooong-EZ/20B Infinity R/G Chpts 18

Velocity/RG N951TM

Mann's Airplane Factory

We add rocket's to everything!

4, 5, 6, 7, 8. 9, 10, 14, 19, 20 Done

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

No insult offered, none taken.

But the difficulty is the reason for looking at alternatives. Although I certainly studied optics in university, its not something I would consider one of my strong points. Software though... I can do that! Why make it tough when I can make it easy? (also known as "when all you've got is a hammer...")

 

 

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'm not sure you do have the EFIS. Not all EFIS have an extra video-out to attach an external screen, most need to be mounted with a particular orientation, and none of them are, AFAIK, specifically designed with output that will translate well to a HUD. To get a nice HUD, we are likely going to need to do some fancy foot-work somewhere. I see 4 general options:

1) Find an EFIS where we have sufficient customisability to choose colour-schemes, and probably eliminate some info so that the HUD is readable and not too cluttered.

2) Try to correct for the non-optimal colour-scheme using optics

3) try to correct for the non-optimal colour-scheme using electronics

4) build our own EFIS.

 

 

 

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.....

Why not just use a monochrome screen? Are you hoping to eliminate the artificial horizon?

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The simplest solution would be a half mirror on top of the glare shield, display buried down behind the IP. Some type of dichroic would be better if you only put a single color on the display and went with a dichroic coating in that narrow range; less attenuating than the half mirror.

You could buy the optics from a 99 or later corvette HUD to get the correct apparent distance.

Unless you have the need to display text you won't have to worry about reversing everything on the graphic display.

...Chrissi

CG Products

www.CozyGirrrl.com

Cozy Mk-IV RG 13B Turbo

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i just emailed Mountainscope to see if he can remove the terrain rendering and go with a single color for the pitch ladder, airspeed and altitude and horizon line.

 

i just found out that the dynon has an output for attitude data, etc, etc. Mountainscope can receive these inputs and display accordingly.

 

SOOOOOO, all we need is a computer to run mountainscope and an LCD panel that can be backlit with an adjustable brightness bulb.

 

Given all of this, the trick is the optics.

 

1. how do you focus to infinity?

2. how to fix the ghosting issue?

 

fixing these two items will result in a HUD (at least....i think it will, ha.ha)

 

anyone have any idea on how to focus the displayed image to infinity? i am totally ignorant to how lens work, especially on this level.

 

i have purchased two beamsplitters from Anchor Optics. they are really nice and seem to work well, they just need an anti-glare coating.....

 

any other ideas?

 

jeff

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I believe i finally have a miniscule understanding of how to focus something at infinity. Basically, the object is our display output, probalby a bright LCD and preferrably monochrome.

 

The first lens (I think it's called the object lens?) is placed so it's focused on the screen. If you were looking directly through the lens at the screen it would be in focus.

 

The image projecting from the lcd and going through the object lens will then come out focused at infinity. That hits the mirror and voila you have an image focuses at infinty

 

The trick is to have the right lens and I think a fresnel lens is where I'll start. I'm going to buy a couple of different cheap lenses of varying ize and focal length and do some experimenting with all this. If I've got it right then it's only a matter of settling on the right lens and mirrors to achieve a decent image.

 

Anyway,

this is all "Ed-theory" and is worth about a wooden nickel.

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OK, I HAVE GREAT NEWS!!

 

i have been in contact with Mountainscope and they have agreed to re-write their software to our purposes. This would involve removing the terrain and switching the airdata and pitch ladder as well as horizon bar over to a "night time" mode which would be essentially "line drawing" data.

 

this system gets it info from the Dynon AHARS. the dynon connects to your computer (running mountainscope) via a serial cable. the computer would then output the data to an LCD panel in the HUD assembly....

 

just need to solve the optics issue (and it sounds like a few of you are working on that).

 

if you are seriously interested in this project, please contact me directly on my yahoo email account:

 

jeff122670 at yahoo.com

 

Jeff

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Ok,

I'm taking a plunge...blindly...

I've bought a couple of smal, inexpensive fresnel lenses. I got 3. They are all 5"x5" and have avrying focal lengths. 2", 5" an 8". I want to see the difference in projected images using the different lenses.

 

I'm goign to use glass with various levels cheap tinting for my initial mirrors.

 

I'm currently looking for a small display unit. I'd like to find a monochrome display with it's own lighting...the Planar displays are gret but I'd rather not spend 500 bucks jsut yet... I'm only doing concept stuff for now.

 

Any ideas on a display unit?..If worse comes toworse I'll just build a small test program to run on my computer CRT and black out everything but the area I want to test platform to project..

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i would suggest using a computer monitor (that is what i did for initial testing)....

 

that presents a decent image to be reflected into your beamsplitter and, although it isnt completely "daylight readable", it will serve the purpose for this test.

 

please email me directly.....i am extremely interested in your results!!

 

email me at:

 

jeff122670@yahoo.com

 

thanks!

 

jeff

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While waiting for my lens order to get here I've been looking for info on mirrors. Specifically I've been looking to see what kind of mirror I would use as the imager.

 

Chrissi's idea about a dichroic looks like a really good idea. I again know aquat about dichroic filters but Wikepedia is very helpful. Since I've been looking towards a monochromatic HUD it seems like a dichroic lens would be a really interesting option. Depending on cost (and apparently good dichroic filters can be very pricey) a lens that reflrects just my symbology could make for a really good display..

 

Anyway, more random thoughts and ideas.

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here is some news..

 

i was looking at my beamsplitters (purchased from anchor optics).

 

i noticed before that there was a ghost image in the beamsplitter and could be mitigated by an antireflective coating....

 

welllllllllllllllll, i turned the beamsplitter around (image reflected on the opposite side) and what do you know, ghost image GONE!!!

 

seems as though these beamsplitters are already coated.............GREAT NEWS.....and the reflected image is much brighter!!

 

still need the lens issue solved....

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Yes, you need to get the right side of the plate facing you =)

If at any time you are unsure just hold it at an angle and look across the plate towards the far edge; on the uncoated side you will see both edges, on the coated side just the one edge.

You need to be straight about the difference between a true EBC (electron beam coated by vaporized metal deposition) coating and partial silvering (usually aluminized) coating. The partial silvering, sometimes called a half mirror, acts like a wide spectrum ND (neutral density) filter and attenuates all visible wavelengths by the same percentage, a dichroic tuned to the right wavelength will be narrowly selective to whatever wavelength you select; red, green, blue, yellow, cyan or magenta.

Realise that whatever you choose is going to pass one color and reflect its complimentry color. You want to be tuned to the reflected color. BUT depending on the strength of the coating the image you see through the plate is going to be slightly off color. This may or may not work to your advantage depending on choice.

My guess is you want mostly glass with a small amount of coating.

The corvette works because you are within an enclosure, the glass is tinted a bit, interior glare is minimized, the plain glass windshield is relatively flat and at an optimal angle to reflect the HUD.

I honestly do no know how the interior of the Cozy will compare. The refractive index of plex is lower than auto glass and its curvature rules out reflecting off of it so you will need the plate. You will want to protect the plate when not in use with a dust cover. Dichroics are delicate, do not touch with your fingers. Cleaning optical plates is not fun, don't ask :)

 

...Chrissi

CG Products

www.CozyGirrrl.com

Cozy Mk-IV RG 13B Turbo

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Share! I've been looking for a place to get that from....Granted I've bene looking for already coated surfaces but anything would do...

 

Also, sorry to be thickheaded but I want to be sure I have this straight...With a dichroic coating you can limit with wavelengths get reflrected. So, If I had a 20% reflective beamsplitter it relfects 20% of the visible spectrum. My question is, if I add a dichroic coating to reflect green, does it only reflect 20% of the light in the green spectrum ? Or, do I actually need a dichroic filter plus the beamsplitter. The dichroic filter would be between my collimator and the beamsplitter and would only allow my green wavelengths to pass to the beamsplitter?

 

I'm startign to see why HUDs aren't common. This is a pretty technical beastie.

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Chances are a piece of plain glass with no coatings would work under ideal conditions.

What you are trying to do is enhance its properties without taking too much away. In other words gains come at a price.

If you wish to enhance its ability to reflect green then the terrain/sky in front of you seen through this dichroic filter will have a magenta tinge to it. Think of dichroic coatings as selective mirrors. I have a disk of glass with a segment of yellow, cyan and magenta coating, those are the collors you see when you hold the glass so that light bounces off of it, when you hold it up to look through it you see red, green and blue instead.

The dichroic filter is your beamsplitter. Actually when you look through it it's a filter, when you use it to selectively reflect and combine images (scene in front of you plus data from below it) then it is a beam splitter.

Good example; studio TV cameras are huge, half of what you see is the lens, the other half is the actual camera. The full color image comes into the camera and goes through a special prism assembly that three very precise geometric chunks of glass bonded together. the facets of those prisms have dichroic coatings on them to precisly cut out and reflect red, green and blue image information to each of three black and white TV camera tubes. The video information is then processed in parallel for each color. Nowadays you will see video cameras in the store, the HD versions will usually say 3 CCD HD which means there is a beam splitter in there with 3 B&W CCD chips. The big deal is each image device is using 100% of its image area for a given color information. Cheaper single chip cameras, including still cameras have image chips that have a mosaic filter over them so that every third pixel in a row recieves red information, same for green and blue so in reality lets say you had a primarily red image, would it then not really be at 1/3 rd the resolution of a 3 ccd camera?

The difference in resolution becomes apparent when you look at a B&W camera image, you may be lacking color but you have a fine image. Early single chip color video cameras had very chunky pixelated images.

...Chrissi

CG Products

www.CozyGirrrl.com

Cozy Mk-IV RG 13B Turbo

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sorry, i didnt mean to tease!!

 

here is the link for the coatings:

 

http://www.cbs-dichroic.com/

 

thanks chrissi!!! you are explaining it the exact way that i understand it. using the above like, they recommended that i go with the emerald coating which gives a green 45 and when looking through it, you get a slight magenta tint to the outside world.

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Well, I got my fresnel lens and one of my mirrors...The beam splitter was back-ordered. :mad:

 

Now I'm working on a simple contraption to hold the lens and mirror in front of my latop display. I wrote a silly little program that draws some graphics in a 4" sqaure area and I'm using that as my 'output'. I need to come up with some way to fine tune my lens focus but overall the results are promising.

I'm sure I'm going to approach a Rube Goldberg design for my experiment but that's ok...I'm only trying to establish how to set the lens and mirrors up...

 

Once I get this I need to find a tiny and brigt LCD screen as my real output. I was hoping to find somethign witha VGA connector but so far I'm looking at 200-300 bucks for a 4" 320x200 500 nit display unit. I dont want to spend that much jsut yet...

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