Laser HUD idea

[ITman496]

Dunno if this has been done and shot down before, but..

I've been thinking for a long time on how a HUD could be made cheaply. With the power of lasers.

What my idea entails is to coat the front face of plexiglass/glass with a UV reactive coating. Then coat the back face with a UV blocking coating (so sunlight can't make it light up from behind). Then shine a UV laser at it with an XY scanner to make the face glow how you want, and bam. Instant HUD.

Of course a company has been there / done that with this idea, but I've had this idea for a while before I learned of them and I have a feeling they won't just sell it.

My only questions are:

Does anyone know of suitable coatings for both sides? I've potentially found one for the UV blocking, and maybe UV glow paint is enough for the display face, but at the same time it might not be bright enough for daytime use.

Laser XY scanners used for display. I have a feeling that they are difficult and expensive.

note: I apologize if this has been suggested and shot down a million times before, I figured this was the best place to toss the idea around, lol

 

[Speedy78]

I think a green laser would be more suitable for this. The HUD in my aircraft is green. Im thinking an analog modulated dpss laser so you can adjust brightness. Not sure about tje coatings foe this. The galvos wont be too expensive. It would be displaying simple shapes and numbers and what not so probably 12k scanners would be enough. I also think glass (not plexi or acrylic) would be better.

 

[ITman496]

If I may ask, why would the green laser be better? The thing about this is that the color is dependent on the coating, not the laser. So you can't see the laser, you just see the results of it energizing the coating and making it glow. Like those UV reactive paints that are clear normally but glow in whichever color when you shine UV on them.

 

[Speedy78]

The green is more visable to the human eye. Not sure how mine works but I belive its reflected off the glass somehow but allows you to see through it. The uv glow paint would work if you only want to display one image. When switch images, like say a speed in a car, you would have an after glow effect and it would become blurry. It would only work if it was active whrn the laser was on it and immediately faded wto nothing when it wasnt.

 

[ITman496]

Yes, that was my plan, actually. I want to find a coating that glows only when the laser is on it. So nothing glow in the dark, more just the paint, which I do not think stores energy in it.

Though now you've got me thinking of a way to maybe get a coating that only reflects a certain wavelength.. That seems like it would make for a much brighter display.

 

[Speedy78]

Yeah. The glass on my HUD is like a half inch think. It definitely has some sort of coating on what apears to be the outside portion. So it kind of reflects like a stadard mirror (not front surface) where the light goes through the glass, reflects on the inside of the coating on the back, then comes back through the glass. Its not a laser though. With lasers you have to be carefull of not reflecting too much power. Makes no sense to wear safety glasses with something like this. You may have enough reflectivity with an uncoated piece of glass. I guess its something you will have to experiment with.

 

[ITman496]

I certainly plan to experiment on it when I can get some of these coatings in the mail. Thanks for the insight on how a real one works, though. =)

 

[Speedy78]

Some quick test with just a plain sheet of glass and around 70mW of green.



With the flash to simulate daylight



This picture tells me that the back side needs to be coated with an AR coating suitable for 532(or whatever wavelength you choose)



And this problem needs to be solved. Somehow block transmission through the glass. While not creating anymore reflection back so you don't get double images. I think it will have to be a combination of AR coatings and maybe something else? Maybe someone can weigh in on this.



Edit: Last picture reminded me to change the calendar. I guess its been a while huh? hahaha

Double Edit Possible scansets for your build

 

[ITman496]

Wow, that is really helpful.

That is one of the reasons that I was leaning towards the idea of a uv reactive coating (well that and I didn't realize how well just hitting the glass with a laser would work)

Maybe less power and something that reflects or absorbs 532nm on the front so that you don't get a double image? I dunno. Can you even get coatings like that to just put on things?

Also yeah, I definitely need to do some research into scanners since I know zero about them.

 

[Speedy78]

There has to be diy coatings available. Or maybe you can buy the glass allready coated from somewhere.

 

[ITman496]

I'm just trying to figure this out.. do you want an AR coating? thats anti-reflective, right?

so an AR coating at 532 would bounce 532 off and let everything else through, or would it do the exact opposite?

 

[Speedy78]

Yeah anti reflection. It would not let 532 reflect back. Hence the anti reflection. It would most likely have to be used on the back side of the glass so that you get some reflection of the front and zero from the back. Or Ar coat the front and have it reflect of the back. Though im unsure of if it would mess up transmission coming back through or not.

 

[ITman496]

I wonder if they have coatings that would /only/ reflect a certain wavelength.

 

[Speedy78]

Im sure they do usually they are 808 1064 532 AR costed for the dpss process. So no idea.

 

[ITman496]

ah, okay. I'll keep looking around, in that case.