Car Head-Up Display

[canadianpoet2012]

I am thinking of trying to design a head-up display for a car. The optical sort that gets projected onto the windscreen, like fighter pilots have and some high end cars now come with.

Does anyone know how they work? Mainly, how you get the projection onto the windscreen. I think obtaining and processing the information and signals for speed, fuel, revs, etc. would be fairly straight forward. The tricky bit is the optical projection.

I haven't really got any ideas as to how to go about this yet, so any comments or suggestions would be most welcome.

 

[Oznog]

I believe they use a special coating on the windshield.

You might need a display with high intensity backlight, maybe a CCFL would do? I don't know. Night's one thing, being daylight readable is quite another thing entirely.

 

[Eclipsed]

I've made several.I use VF displays and mirrored plexi-glass/Lucite to reflect the image onto the windshield.The VFDs are bright enough, so you don't need any coating on the windshield itself.

 

[canadianpoet2012]

Oznog, I did think that I might have needed some sort of special coating. Either super reflective, or slightly frosted.

Eclipsed, I am very interested in your reply. Could you give me more details about a VFD. What is it, and how does it work? How do you actually produce an image on the glass? Is it solely by light displays, LEDs behind a lens for instance? Or do you have some sort of software running a program that produces images to be projected onto the glass? Is it a hobbyist’s project, or have I bitten off more than I can chew again?!

Thank you both for your replies though.

 

[bmcculla]

Normal glass has about 4% reflectivity at 0 degrees incidence so you should get more the higher the angle. There should be no problem at night but in bright sunlight it will probably be hard to see. VFD (vacuum fluorescent display) can usually be driven in the same way small LCD displays are driven. Noritake makes VFD that are designed to be direct replacements for LCDs. You will probably need some optics to focus the image at the appropreate distance in the drivers view. The optics design in this project is going to be the most difficult part. Driving the VFD shouldn't be that hard.

Brent

 

[Eclipsed]

Noritake are the displays I use.They have a full line with parallel interface, as well as some with a serial interface.Their serial displays are becoming harder to find in small quantities.They seem to pop up on Ebay once a month or so, and for very reasonable prices.As far as optics, after you get the angle correct, they will project very well, even in sunlight.My guess is, its the safety laminate in automotive windshields that helps reflect the image.If mounting options limit the possible angles, you can put a small piece of aluminized(UV protected) window tint in the projection area.