I did see some units in the $100 range, but they were all 640x480 (or less). The higher res ones seemed to be more money, although I did not look for very long.

Not sure if that reflector would work, but you can't really go wrong at that price. I did read that type of material (like the RR tape, stripes on jackets, etc.) are designed to be slightly diffuse and not a perfect retro reflection. I think they said the reflection angle would be +-3 degrees. They do this since the main application is for driving safety, and a perfect retro reflector wouldn't work. If it were perfect the beam of light would only reflect directly into the car's headlights and not be visible by the driver. So there must be some leeway. This of course is not what we want for precise optical applications. However for a quick proof-of-concept, it might suffice.

The xga i refer to is just upscaled from vga of course but still handy for fitting menus on screen. I agree those reflectors wouldnt be much good, would just give a colored smudge.

Further thinking.. Do we really need an RR for this to work? It should work with a normal piece of projector material as we are just looking at the reflection of that from the glass. The killer will be the light loss which is maybe why the RR is needed to boost the light reflection. If we use this as a HMD and not a see through AR device it will be enclosed so the light loss should not matter as much.

Got to get of my butt and do some testing...

Yeah, we do. If we use a regular mirror, and focus the light into a small area (like in my diagram) then it will reflect getting smaller. I guess if you set it up right this could work (as it would eventually reverse the image and get bigger again) but the image would be backwards. Using a projector screen material would also somewhat work, but it would be no different then just strapping the projector to a helmet and looking at the wall. Although I would be interested to know what method they are using in this video:



Seems like they are just projecting directly on a piece of glass using a laser projector. Does that work? Why doesn't the image just go through the glass?

I ordered a ShowWX yesterday, I am going to be running a barrage of tests on it. I will let you know the results.

I might even try retinal projection. Turn it to the lowest brightness setting, and apparently the new firmware allows for individual RGB level controls. Going to turn all the levels to minimum, then use my LPM to measure the combined output of the projection. If it is under 5mw on a point, then I will be shooting it into my eye.

Do what I do, when trying retinal projection, put 2 sheets of polarized material in front of the lens, change the relative angles to adjust the brightness.
My experience is that the exit pupil in minuscule.

Yes it'll work, with a rather large loss of brightness.
All glass is a specular reflector at none 0 angles of incidence, a lot of light will go straight through though.

Good luck man. I sincerely hope you know what you're doing.

Not sure if this will help but this projector is about $300 can do Resolution: 1024 × 768

http://www.walsoon-tech.com/en/index.ph ... &Itemid=82

If anyone get round to making a high res, high FOV HMD. Have got cash waiting for 1000 units. I'm serious. Price needs to be sub $1000. PM or write here for contact.

I've tried white/silver retroreflectors and the issue is that the standard diffuse reflection washes out the retro reflection.
It'd probably work better if the retro-reflector we're further away, since that would reduce the ambient reflection, but shouldn't affect the retro-reflection.
I've ordered some black retro reflective material to see if it's any better.

I have my black retro reflector, and now I think the white/silver ones are probably fine.

My understandong of the optics was somewhat flawed, I need to sit down and draw some to really understand what's happening.
I need to build a more stable bench prototype, but doing some hand held tests last night, as far as I can tell the following is the case, the projector has to focus on the retro reflector (practically this isn't much of an issue). But the image seems to appear in focus regardless of the focal point of the eye, if you don't use a retro reflector, you have to focus at the effective depth of the screen.

This is not what I expected, as I said I need to do some more testing, and I need to understand optically what's happenning.

I should note that what I'm observing with tests is still promising, it's just not what I expected.

I have played with retro-reflectors, but not in relation to VR. Rather, I was working on a project to put a laser beacon on a robot, and then when it hit a retro-reflective target, the reflected light would be sensed by a photo transistor. This would be used to calculate an angle between the targets, and then used this data to determine location.

Sorry for the long 0ff-topic explanation, but the point was to say that when I used a single point laser, the reflective
light would trigger the sensor very on-off-on-off, etc. This was because there was a grain to the reflectors. As the laser hit one spot, it would be reflected strongly, but then slightly to one side, the reflection was aimed off a slightly different direction, and not sensed. I solved this by putting a beam spreader into in to generate a fan of laser light. But, this created some of its own challenges.

I used some retro-reflective tape I purchased at Walmart, designed to be applied to things like trailers. What exactly was the source of your retro-reflective material?

Joe Dunfee

I think you can also use a corner-reflector for the same purpose as the retro-reflective material. In this case you can just use standard 100% reflective mirrors so they should be optically accurate.

It's definitely acting as a retro reflector, if I put a Lens between the mirror and the screen, I can see it distort the edge of screen, but not the image. which us what I would expect.
It's just the way I read the original diagram in the papers is incorrect, I need to think about what I'm seeing.
The grain is clearly visible on all of the retro reflectors I've tried. A corner reflector is an interesting idea.
One of the bigger packaging issues is going to be the short throw of the projector, you really want optics to give you a longer throw, or the projector has to be right on top of the mirror.

Cyberreality, in my case I had one more complication that I didn't mention. I was planning on doing barcode with the reflective tape. So, a corner reflective would not work in that case. I think the tape is, in essence, a bunch of tiny little corner reflectors. Some of the brands I have seen are coarser grained that others.

Joe Dunfee

OK after further messing around, I think it is working the way I originally expected.
The issue is the diffuse reflection is sitting on top of the retro reflection, and the projector is so bright, that it's hard to differentiate.

I just did a simple experiment to get a feel for this idea as seen the the picture below.
At the top is an lcd (i used my phone) shining down through the clear cd lid, it then reflects off the mirror at the bottom back up onto the eye side of the cd case which is viewed as a floating screen through the cd case and is the correct orientation (not reversed).
This in itself is like looking at the phone normally except that it is not as bright. The only geek use is that this is now an Augmented Reality device as the screen is superimposed over your normal view. The down side is you cant see it in daylight because of the brightness. Im considering options to use one for each eye but one up, one down to make size for bigger displays that would normally clash if side by side.




I then added a magnifying glass on top of the mirror and it did add some decent size increase to the image as expected. The result with my 2.5 inch phone lcd was a deal bigger than the vr920 view.




I then tried replacing the lcd with a pico projector. This didnt work for a few reasons. Firstly it projected a reflection directly from the cd case onto the wall i was looking at (in reverse). This might not be so bad for AR as long as you dont get to close to something or someone. Secondly it just reflected tons of light straight back into my eye like looking straight into the projector. This has me still wondering what would be the result with an RR instead of a mirror.






Now my understanding of the full concept is that the only reason the RR or mirror is used is to correct the orientation of the image so it isnt reversed. I am still not sure that an RR is needed at all rather than just a mirror and the correct glass/filter/lens combo.

Hmm, interesting. Looks like the method still needs some work (or rather, maybe the 50/50 mirror and RR are more essential than you think). Although, if you are getting a bigger image than the VR920 even with such a make-shift setup, we are at least getting somewhere. I'd like to hear how this progresses.

Epiphany!!!!

Sorry if this is getting too off topic (should i make another thread?) but after dwelling on my last post i have had this idea.


Note i haven't done a mockup of this yet but its using the same idea as before but with added magic (yay magic!).
Firstly instead of up/down its side by side. Its basically a method to use 2 large lcd's (4.5" maybe) with twin mirror method because of side by side size constraint. We know 2 mirrors are required each side to move the image AND correct the reversal. But this uses instead the 50/50 glass as one of the mirrors. The difference here is that because of placement you can see the lcd's through the glass but you dont want to. This is what the polarized filters in front of each eye are for (not sure if more will be needed). Hopefully they will block the direct through glass view and only allow the 'virtual' reflected view.

Playing with sizes/positions this may give us a healthy FOV reasonable res hmd.
I feel all excited about this like i should patent it lol. This could be a big ugly but useful rig for under 1k.
What do you think?

Ok, that looks like a good idea. However, what is the point of having the lens right on top of the mirror. Wouldn't it work better it it was right in front of the LCD or right in front of your eye (ie in a position that light only passes through once). If its right on the mirror, the light would pass through and then bounce right back effectively negating the purpose of the lens. Right?

I think you'll have to move the displays out of the line of sight , because the two images won't line up.

True. I didn't even notice that. You would be seeing some *serious* ghosting if the LCD was in your line-of-sight.

Thats what the filters in front of the eyes block out, the actual lcd screen. If it works out that it also block the virtual screen a second filter will be needed over the mirror maybe.

This setup is not for AR, this will be enclosed.

Interesting, missed the filters, then yes it ought to work although I think you'll need some way to additionally rotate the polarization of the final image.
You have 2 bounces off mirrors which will leave you where you started, I think...

Very interesting topic. I think maybe just remove the mirro, let the

beam project on 45 degree tilted semi lens through a convex lens which

can make the projector's focus lengh just right, i mean using the semi

lens as a projection screen, but we can stll seee through it. So, we

finally get a mixed view. It's very like Apache HMD, it's my imagination.

Okta, can you try what i wrote? If it work fine, i'm going to build one.

John: My previous test with a projector shining onto the beam splitter just made the light reflect into my eyes like a torch without any image. What did work was shining the projector through a beam splitter onto a screen surface, that image is then seen as a virtual screen through the beam splitter. This would certainly be the easiest way to use pico's in a DIY HMD i think although it is difficult and bulky still to get a large FOV.

Get your phone and a clear cd cover or glass sheet in a dark room to experiment.

I tried what you said. I can get a clear image in my eye through the reflection a CD cover in dark room. But the problem is that image of my cellphone is not projected from infinity distance which meas my eye can only focus on cellpone image or outside object, not simultaneously. I can not get a focused ,mixed image and clear image.

any idea of this?

I hadn't really thought about that as i intended to make a closed system anyway. I dont see how that could be done? At the end of the day it is the lens on the eye that focuses a set distance for the retina so i cant see how it could be done?

Oh, i also used a mirror and had the cd facing away in my test as per my pictures before, that make the screen the correct orientation.

If the plastic reflective surface is curved to create a slight magnifying mirror effect, then your eye will be able to focus on the image as though it were further away. As long as the plastic is relatively thin it won't affect focus onto distant objects.

Now, getting a proper curved shape is another issue. Perhaps a magnifying mirror can have its reflective surface removed, leaving you with a curved glass. But, I have doubts the curve is the exact curve necessary. But, it may be good enough.

Joe Dunfee

it seems the Japanese has just found the way. Their new product airscouter is just what i want. but it's extremely expensive.

http://www.youtube.com/watch?v=9I0hF0cbw8E

anyone has any idea how the projector of airscouter works?

The Airscouter is monochrome, low FOV, and does not use any real novel design. We have a few threads about it if you search, but basically, it uses a scanning image projection element that is very similar to the Private Eye P4, or the Virtual Boy.

this makes an interesting reading, may give people some ideas..

That is the patent that the Headplay uses. It is interesting, but not really suitable for the kind of stuff we are making.

can you give me some more info palmer ,ive been looking around for a diy hmd and still not sure what the best way round to go debating on single display similar to what you have done , or twin displays mirror no mirror ,fresnels leep optics ,its all abit confusing which way to go, also its ni on impossible to get leep optics anywhere no one seems to sell anything similar very frustrating..

ps have also been looking at pico laser projectors because they never go out of focus so you can have a curved suface then maybe put right with warpilizer software thew my brain hurts