Display on a curved, transparent surface.

For a motorcycle helmet windshield. Avenues I checked are laser projection through a transparent LCD or a transparent LCD attached to the windshield. Any ideas on feasibility? or maybe other avenues to check?

dd_dent:
For a motorcycle helmet windshield.
Avenues I checked are laser projection through a transparent LCD or a transparent LCD attached to the windshield.
Any ideas on feasibility? or maybe other avenues to check?

Maybe an LED micro-projector? You couldn’t drive it with an Arduino (typically needs VGA input), though…

I’ve never worn a motorcycle helmet, but you might want to first see if you can focus on an image at the “plane” of the faceshield; if not, you will need optics to focus the image. Something else to think about is whether the curved surface will present an issue with distortion (for the data you plan to display); if so, you will need a method to cancel that as well (optical or in software).

You’re going to need something that allows you to focus your image far beyond the plane of the windshield. Anything will put up an image that you would look through directly is right out, as well as anything projecting focused on the plane of the windshield itsself. For the easiest example of why this won’t work just take a dry erase marker and draw some things on your windshield and then try and read them while actually using the helmet.

MotionResearch made a helmet mounted HUD a few years ago, but it seems like a totally dead company these days.

If dreamed of making something like this but for cars, a HUD , heads up display , it does require a lot of focusing so it is readable also the glass/plastic has to be coated with some something , i forgot the name, which still alows you to see but also reflects the light in a way where it will not just pass right through or bounce and blind you.. look into the Corvettes HUD or military aircraft hud readinh up on that will give you some ideas.

First of all, thanks for all the feedback!

extent: You're going to need something that allows you to focus your image far beyond the plane of the windshield.

Is this even possible? And if so, where can I dig up the required numbers and equations for this? Also, does it rule out taping a transparent 7-seg display onto the windshield itself?

http://www.dealextreme.com/p/tiny-projection-clock-keychain-1489 I took apart one of these things: It's composed of a tiny TN-LCD without the usual opaque cover on it's back (hence transparent), a laser diode and a plastic lens. it can be projected on the windshield, although I haven't checked visibility in daylight and I didn't tried viewing it from inside the helmet, but as you said, it can be refocused(?).

dd_dent: First of all, thanks for all the feedback!

extent: You're going to need something that allows you to focus your image far beyond the plane of the windshield.

Is this even possible? And if so, where can I dig up the required numbers and equations for this?

Yes - perfectly possible; as far as equations and such - that's a completely different matter - you're going to want to get into the "down and dirty" details of HUD (Heads Up Display) and HMD (Head Mounted Display) design. There are a lot of research papers and other information out there if you dig for it (a lot of it is hidden behind paywalls and other "barriers", unfortunately - so expect to spend a lot of time and money). If you can get hold of some old back-issues of PCVR magazine, there was several articles on HMD design. Also - check out various old homebrew virtual reality books from the 1990s.

Ultimately, though, it's all optics and such - so any good book or other resource on optics and the math that covers all that will help (you might start with a high-school physics textbook, for instance).

dd_dent: Also, does it rule out taping a transparent 7-seg display onto the windshield itself?

Without optics, most likely - your eye will not be able to focus on it for very long, if at all - without causing massive eye-strain, headache, possible nausea, etc...

dd_dent: http://www.dealextreme.com/p/tiny-projection-clock-keychain-1489 I took apart one of these things: It's composed of a tiny TN-LCD without the usual opaque cover on it's back (hence transparent), a laser diode and a plastic lens. it can be projected on the windshield, although I haven't checked visibility in daylight and I didn't tried viewing it from inside the helmet, but as you said, it can be refocused(?).

Yes - if you are willing to spend the time and effort to do so (assuming it has enough brightness, etc - as you've noted).

This isn't going to be an easy project at all, know that. I am also wondering whether you have checked with the laws in your local area regarding such a system in a motorcycle helmet (and I mean really check - talk with a lawyer if you have to). It might be legal to have such a system where you're at; it might not be. It might be that the company extent referred to earlier with a similar helmet went out of business because of the law, or because of the patchwork of laws - that made such a device difficult or impossible to sell.

I could see such a display as being a hazard; impairing vision (especially potential peripheral vision), being a distraction, etc. Such devices might be "banned" due to these and other potential issues. Just something to keep in mind before you spend a ton of money on such a project.

Links and information to investigate:

http://en.wikipedia.org/wiki/Motorcycle_helmet http://www.nhtsa.gov/Safety/Motorcycles http://edocket.access.gpo.gov/cfr_2007/octqtr/pdf/49cfr571.218.pdf http://www.smf.org/ http://www.smf.org/standards/m/2010/m2010_final_booklet.pdf

I would say contact both the NHTSA and SMF (if you're in the US; otherwise contact your local equivalents) directly for more information on what you want to do; I must say that with the minor research I did finding the above links, most everything pointed to the fact that users should not modify their helmets in any way, as doing so could cause safety and/or structural issues.

If this is just for a non-wearable prototype to investigate the idea of manufacturing (and getting certified) such a helmet - that's one thing. But if you want to stay safe in actual practice - I wouldn't modify a "daily rider" helmet.

Your head and brain, though... :)

I'm very much interested in this idea as well since I ride and would appreciate being able to get my RPM and MPH without having to look down away from the road. (In San Antonio, you may as well be invisible while on a motorcycle.)

What you want to do to the image (light) is collimate it. This will present the image as though it is coming from far away. This will prevent your eyes from having to focus really close then really far. There are cheap but bulky methods of accomplishing this and small, lightweight and EXPENSIVE ways of accomplishing this. (I've been doing a lot of reading.) For the definition and implementation of light collimation, start with the wikipedia page for lenses and then for more reading fun, you can crack open a physics textbook. (Although, my text did not provide much information beyond the basics of optics and all the ways to make your head hurt while solving problems. Collimation was basically defined then passed over.)

There is a company that manufactures a VERY NICE piece of equipment for skiers/snowboarders called Recon Instruments that projects a screen with a lot of info that a motorcyclist simply will never need but they do accomplish the physics and they do it with a small package. Unfortunately, it is a $300 minimum to play and aside from not being able to use most of that info, it's pretty expensive. Add back to it the fact that most of the "features" are useless to a motorcyclist and the price goes up even further I would love to play with one though. They make a $400 unit that can apparently be developed for (Android OS), but still too expensive for most average folks. Especially average folks that cannot use all of the base features. Seriously, they might offer just the display apparatus for a reasonable amount and turn people loose with it. (Ideal for me!)

Good luck! I hope you're able to get something put together. I'll keep an eye out for your progress!

Allen