Project NiteVision - NiteMax + HUD + carputer

**shotgunefx** · 08-12-2006, 04:52 PM

Originally Posted by alpha_maverick

a combiner is the same as a beamsplitter. 50/50 means that 1/2 is reflected and half is allowed to pass through. some are directional, meaning that from one direction, nothing (not much) is reflected, but from the other side, it's half and half. http://www.edmundoptics.com/onlineca...productid=2035

Reflected and projected are the same thing!!!! you are not focusing the image on the plate! you focus it on your retina (or near it)! you align the optics to reflect the light so that it is (relatively) square to your eye-level and adjust the focus so that the image appears at the end of the hood, etc. kinda like the focus knob of binoculars.

GTG, more later

If you read up on some of the combiners in use, in particular the military stuff, they aren't simple planes, often they are curved and laser etched, ie, way way out of our league.

I understand that projected and reflected light are the same, the difference I'm getting at, if you lay an LCD on your dashboard, you'll see the LCD on the windsheild, pretty much focused. Yes light is emitted and that's what you're seeing, but what you are seeing is the source, so there is nothing to get rid of.

If you project the image onto the glass from behind you or (anywhere close to it), you will see the reflection of the projection source itself. There's the rub. Light is light, I don't see how you can make the emitter disappear and not what's emitted. I think the best you can do (on the hobbyist level) is get it out of the field of view.

All the huds I've seen that are on cars are basically VFDs or similar, your not seeing it projected through a lens so to speak, it looks like they are just reflected off a window.

**alpha_maverick** · 08-12-2006, 09:01 PM

if you look at the bottom of the beamsplitter page I linked to, there is a plate that would be approximately the appropriate size for our application, and it is flat. I was proposing what others were: hide the display assembly in the dash. Something that just came to me: Why could we not use a small sheet of privacy glass to guard the expensive LCD and lenses? put the privacy glass on the dash as a dust/light cover for the lense and LCD, and put the LCD/lense assembly latterally across the inside of the dashboard.

what you are seeing as "reflected" is just an unmodified focal length (distance from eye to glass+distance from glass to LCD) The lense assembly allows you to extend your focal length beyond the glass, out to infinity.

would that not work? I know it would be large at first, but as "we" progressed (I will not be able to assist, except with the theory of stuff), the package would get progressively smaller.

**Yevmeister** · 08-12-2006, 10:27 PM

sounds interesting, the only things is how would privacy screen protect the lcd, when at some point sun would beam, though the lens on lcd,

Yev

**alpha_maverick** · 08-12-2006, 10:42 PM

when you shut the car off, the privacy glass would turn off, going translucent, keeping (most of) the light from getting to the lense aray, and burning the LCD. When driving in direct sunlight... wait... is there a way to have an electronically adjusted tint, like on new cars interior rear-view mirrors? What about a light diode/check valve? Nevermind on that one. Perhaps it would be better to just put some sort of fans on the LCD, to prevent it from overheating, like on projectors, and just ignore teh privacy glass.

side note: only half of the sunlight will reach the lense/LCD array, the other half will be largely cancelled out by the AR coating on the back of the plate, since it was supposed to be reflected away (forward).

To bypass these needs, you would have to project from above, rather than below. That doesn't work for most of us, though.

**Yevmeister** · 08-12-2006, 10:50 PM

gotcha, well the fans are a must no matter what, if you will use a projection source

Yev

**Yevmeister** · 08-12-2006, 10:59 PM

like i have stated in my previous post, you can also have a flip holoscreen, with rear view projections

**Genesisfactor** · 08-12-2006, 11:05 PM

Tint adjustmetn is done by slightly shift polarized elements i beleive. I knwo what your'e talking about, but no, now thngs are getting too "hi tech". A simple motoized cover, PIC, and a photocell will do the trick quite nicely. See, the sun is a major reason why i DON'T want to use magnification. I would rather do a reflection, but in all honesty, with a 2.5" LCD, i have no choice. The one thing i'm still wondering is how to fit al the elements in the top cover of my gauge cluster. THe LCD would be hard enough, but a magnifying system...

Anyways, lost in thought, alpha, listen, i will not say it won't work, nor will i say its impractical, nor challenge you in any way. This is a real find. But i woudl ask that you come up with something for us. lol, not a working prototype, but, as its been said before, we need all the minds on this as we can get. i want to see your findings in yrou research, even if you ar short on cash. maybe you can guide us/me.

.

**shotgunefx** · 08-13-2006, 12:09 AM

Originally Posted by alpha_maverick

if you look at the bottom of the beamsplitter page I linked to, there is a plate that would be approximately the appropriate size for our application, and it is flat. I was proposing what others were: hide the display assembly in the dash. Something that just came to me: Why could we not use a small sheet of privacy glass to guard the expensive LCD and lenses? put the privacy glass on the dash as a dust/light cover for the lense and LCD, and put the LCD/lense assembly latterally across the inside of the dashboard.

what you are seeing as "reflected" is just an unmodified focal length (distance from eye to glass+distance from glass to LCD) The lense assembly allows you to extend your focal length beyond the glass, out to infinity.

would that not work? I know it would be large at first, but as "we" progressed (I will not be able to assist, except with the theory of stuff), the package would get progressively smaller.

The problem I see is that you will see the light source as well as the projected image. Regardless if the beam is split. If half of the image is directed towards you and half away from you, I still think you'll have the same problem at half intensity. Because the projected source is split too.

I guess what I'm getting at is projecting it is like a point source where a reflected LCD is more like an orthogonal projection.

Like this pic from earlier..

It's just a projector hacked from an old camcorder viewfinder. It's projected through the fresnel and then onto the wall. Notice how you can still see the projection source at the bottom left? If I were projecting onto glass (after the fresnel), you'd see it there too IIRC.

I'll have to find my stuff and give it another try.

Also, that privacy glass (electrochromatic glass IIRC) that your thinking of, I once looked into it awhile ago, dont' know how practical it is. It's real expensive, but it's also a current draw. I door would probably be better.

**quantum** · 08-14-2006, 09:52 PM

Hey all,

Came across this if anyone's interested on E-bay

Short throw motorized projection lens:

http://cgi.ebay.com/Short-Throw-Lens...QQcmdZViewItem

Partstore.com has it listed for $800.00.
http://www.partstore.com/ProductDeta...1455&s=froogle

I bought one off e-bay for myself for $25.00 shipped. If nothing else, maybe I'll make a projection TV for my den.

Guys, I am also really digging the holo-display panels, going to do some experiments this weekend with a rear projection night vision setup...

GF - as far as I know, all polarized films have some color to them, never seen one crystal clear, although some sites claim they are, not really...

**Genesisfactor** · 08-14-2006, 10:16 PM

crystal clear would be nearly impossible, wouldn't it? I dunno, i'm trying to find the pinouts of the RCA in of the LCD still. I got my s-vid to rca adapter today. Go ebay.

Forgive me, but i'm not all there today....how wouuld you utilize the lenses withthe projection. Yeah, i'm really not there at all today...

\BTW, 512K of RAM means its time for an upgrade

. Change it quick, i won't tell anybody!