[REQ] Home-made planar - looking for more information

Post by **The_Doctor** » Sun Sep 14, 2008 12:51 pm

Hi everybody,
I did read stuff around here but it's not 100% clear yet, so if anybody got nothing better to and can explain this some more I would appreciate it.

I have a 24" lcd that has been sitting in a backroom somewhere b/c I have been using a crt with the old nvidia drivers and now the new interlaced iz3d driver. I thought maybe I should build a planar to see what it is like.

1.) I hooked the 24" lcd up and looked at it with some polarized glasses that "have lenses specially cut at opposing 45° degree angles. (these ones - http://www.berezin.com/3d/3dglasses.htm#Polarized: 3D Polarized Aviator Style (Now in Tortoise-Shell!) ).
Looking through the lenses while holding the glasses straight I can see through both lenses. When turning them 45 degrees to the right the right lense goes black and when turning them 45 degrees to the left the left lense goes black.
When looking at the laptop screen straight (different screen) the left lense is black.

2.) Another pair of glasses that I have(no idea what they are, but they are different than the first pair) - when I look at the 24" lcd the right lense is black and the left turns black when I turn them 90 degrees to the right.
When looking at the laptop screen the right lense turns black when I turn them 45 degrees to the right and the left lense turns black when i turn them 45 degrees to the left.

What's the polarization of the 2nd pair of glasses knowing that the first pair is 45 degrees? 0 or 90 degrees?

Can I use that monitor for planar with an identical 2nd one and if not what do I need to do to it to get it to work with either pair of glasses?

Thanks

Post by **LukePC1** » Sun Sep 14, 2008 1:51 pm

It seems like you have the right glasses already - the first ones which are 45° (and 135° on the other eye).
Since these are the ones you would need to use, one eye should be black when the glasses are straight. Unfortunatly that is not the case, so the monitor you have has either 90° or 0° polarization.

That means, that if you mirror the polarization it would stay the same

The only possibility is to get second different monitor, where the other eye with the 0°/90° glasses is black.

For testing you could use crt and LCD - if they have nearly same shape and size - and a normal mirror. If you adjust it right, it would give you 1 hotspot, where each eye sees a different monitor and different image. It is not very nice, but works for testing (the driver).

Post by **sharky** » Sun Sep 14, 2008 1:51 pm

hi there!

one pair is -45 +45°, and the second pair 0° +90°.

you have two angles when you have glasses. the first is for the left eye, the second for the right eye. so the first is not just 45° but -45° and +45°.

AFAIK, you cant build the requested rig because you need amonitor polarized at +- 45°... but i nevber built one myself.. you better wiat for somebody more informed..
cu

igor

Post by **maart** » Sun Sep 14, 2008 1:56 pm

use the second pair of glasses ( 0° +90° )
use both the same 24" lcd screens, and what you need is a halfmirror or a piece of glass to reflect one screen

Post by **Likay** » Sun Sep 14, 2008 3:31 pm

I think you need a retarder + an extra polarizer for one of the lcd's if you're using 0°/90°.
If you use 45°/135° the mirror takes care of the shift in polarization (the reflected beam will have 135° if it was 45° before).
You need lcd's with native 45° or 135° polarization for the rig to work without extra retarders and polarizers.
The real expert here is Nubie and he have an excellent planar device himself. Maybe he drops by with some advices.

cheers

Post by **LukePC1** » Sun Sep 14, 2008 3:33 pm

maart wrote:use the second pair of glasses ( 0° +90° )
use both the same 24" lcd screens, and what you need is a halfmirror or a piece of glass to reflect one screen

but wouldn't one eye always see both screens and the other olways black?

You could turn one screen by 90° however. But I think their shape wouldn't fit then

like this:

_
_ I I I
_

Post by **The_Doctor** » Sun Sep 14, 2008 4:28 pm

Thank you all for your help.

So I need to shift the light 45 degrees on both monitors and use 45/135 glasses or I can shift the light on just one of them and use 0/90 glasses? What exactly do I need for both options and how much light is lost (0%-100%) ?

Likay wrote:I think you need a retarder + an extra polarizer for one of the lcd's if you're using 0°/90°.
If you use 45°/135° the mirror takes care of the shift in polarization (the reflected beam will have 135° if it was 45° before).
You need lcd's with native 45° or 135° polarization for the rig to work without extra retarders and polarizers.
The real expert here is Nubie and he have an excellent planar device himself. Maybe he drops by with some advices.

cheers

Post by **Likay** » Sun Sep 14, 2008 4:50 pm

If your monitors are at 0/90 now you could go for the option: Buying a retarder + a polarizer for one of the monitors and use 0/90 glasses.
The other option is buying retarders/polarizers for both monitors and align them 45/135 to get equal light output from each of them and use 45/135 glasses.

My personal advice since it's also the cheapest one: Since you're using a semireflective mirror in a planar device the light from monitors to the eyes might not be equal from the beginning. In that case use the retarder and polarizer on the brightest one to equalize the effect.

The retarder is really cheap to buy but the polarizer cost a little more. Not a biggie in the whole picture though. There are two types of retarders (halfwave and quarterwave) and i tried quarterwave retarders with polarizer with great success! Nearly no light loss when testing to shift polarity 90° on my lcd-monitor.

Note: The retarder is suppoused to be in between the monitor and the polarizer. It also have to be aligned at correct degrees to have desired effect. The function of the retarder is "twisting" the polarization a bit before it's straightened out by the extra polarizer. Using a retarder foil only will not help since different wavelengths are rotated slightly different by the retarder. Therefore you need the extra polarizer.

Hope this have been helpful. This is a solution to get your rig work with 0/90 monitors even if of course 45/135 are prefered.

Good luck!

Post by **The_Doctor** » Sun Sep 14, 2008 4:55 pm

Sounds good, I will look into this, I'll post my results once I get everything together.

Likay wrote:If your monitors are at 0/90 now you could go for the option: Buying a retarder + a polarizer for one of the monitors and use 0/90 glasses.
The other option is buying retarders/polarizers for both monitors and align them 45/135 to get equal light output from each of them and use 45/135 glasses.

My personal advice since it's also the cheapest one: Since you're using a semireflective mirror in a planar device the light from monitors to the eyes might not be equal from the beginning. In that case use the retarder and polarizer on the brightest one to equalize the effect.

The retarder is really cheap to buy but the polarizer cost a little more. Not a biggie in the whole picture though. There are two types of retarders (halfwave and quarterwave) and i tried quarterwave retarders with polarizer with great success! Nearly no light loss when testing to shift polarity 90° on my lcd-monitor.

Note: The retarder is suppoused to be in between the monitor and the polarizer. It also have to be aligned at correct degrees to have desired effect. The function of the retarder is "twisting" the polarization a bit before it's straightened out by the extra polarizer. Using a retarder foil only will not help since different wavelengths are rotated slightly different by the retarder. Therefore you also need the extra polarizer.

Hope this have been helpful. This is a solution to get your rig work with 0/90 monitors even if of course 45/135 are prefered.

Good luck!

Post by **nubie** » Sun Sep 14, 2008 11:50 pm

The glasses should look like this:

I don't know about buying custom stuff, I couldn't afford it for sure (add up a few hundred dollars and I could have a 3D projection rig instead

).

I hope it works for you, I know Likay got something to work. (Why can't they just figure out a reasonably priced high resolution HMD? Use a single wide panel and let each eye see only one side, then we get dual 1280x720. Sell for under $500. Or the same for a DLP circular polarized color wheel, the technology exists.)

Post by **The_Doctor** » Mon Sep 15, 2008 8:35 am

Yep. That's how the laptop screen looks like through the 45/135 glasses, but the lcd is 0 degrees.

It's only a retarder and polarizer for one monitor to change the light 90 degrees and then use the 0/90 glasses, not too much extra stuff, or use a 45 second monitor and change the first to 45 degrees. It seems that I can see the monitor through the 0/90 glasses much more than through the 45/135 glasses.

I suspect this will lead to a lot more ghosting?

What about moving around? Do you have to look straight at it or can you move around? Do you see more ghosting if moving?

nubie wrote:The glasses should look like this:

I don't know about buying custom stuff, I couldn't afford it for sure (add up a few hundred dollars and I could have a 3D projection rig instead ).

I hope it works for you, I know Likay got something to work. (Why can't they just figure out a reasonably priced high resolution HMD? Use a single wide panel and let each eye see only one side, then we get dual 1280x720. Sell for under $500. Or the same for a DLP circular polarized color wheel, the technology exists.)

Post by **LukePC1** » Mon Sep 15, 2008 9:08 am

why not try it out? Just move a little with the glasses on and watching only through the black eye. As long as it stays completly black you have no ghosting. If you see a little light from the screen it is some ghosting.

You can also use SG. They are polarized, too. You will just have to figure out, how to turn them...

Post by **Likay** » Mon Sep 15, 2008 12:02 pm

The_Doctor wrote:Yep. That's how the laptop screen looks like through the 45/135 glasses, but the lcd is 0 degrees.

It's only a retarder and polarizer for one monitor to change the light 90 degrees and then use the 0/90 glasses, not too much extra stuff, or use a 45 second monitor and change the first to 45 degrees. It seems that I can see the monitor through the 0/90 glasses much more than through the 45/135 glasses.

I suspect this will lead to a lot more ghosting?

What about moving around? Do you have to look straight at it or can you move around? Do you see more ghosting if moving?

nubie wrote:The glasses should look like this:

I don't know about buying custom stuff, I couldn't afford it for sure (add up a few hundred dollars and I could have a 3D projection rig instead ).

I hope it works for you, I know Likay got something to work. (Why can't they just figure out a reasonably priced high resolution HMD? Use a single wide panel and let each eye see only one side, then we get dual 1280x720. Sell for under $500. Or the same for a DLP circular polarized color wheel, the technology exists.)

Hm, let's get some things straight here.

If you have the same phenomena as in nubies pictures with 45/135 glasses (aligned horisontally and vertically). I mean one is blacked out and one "fully" let through if the glasses are aligned horisontally or vertically (not 45°). In that case your monitor IS 45/135°. Just to straight some things out.

Post by **The_Doctor** » Mon Sep 15, 2008 12:27 pm

Unfortunately they look like that when looking at the laptop screen and not on the 24" lcd, so the 24" is 0/90 while the laptop screen is 45/135.

Likay wrote: Hm, let's get some things straight here.

If you have the same phenomena as in nubies pictures with 45/135 glasses (aligned horisontally and vertically). I mean one is blacked out and one "fully" let through if the glasses are aligned horisontally or vertically (not 45°). In that case your monitor IS 45/135°. Just to straight some things out.

Post by **Likay** » Mon Sep 15, 2008 12:56 pm

Ok. Sorry, was left behind but now i'm with you.

Meanwhile i made a vid on how a qw-retarder behaves with polarized light. You can also estimate the light loss of using this method here too. A slight extra amount of light can be gained by using 2 qw-foils or one halfwave foil. Just don't have any halfwavefoils for the moment.

Unfortunately i don't have any good tip on which mirror to use or where to find. I had great trouble manage that here (sweden). I had serious plans of building a planar rig once but everything broke because of the hazzle finding a suitable mirror. Just didn't felt for ordering stuffs at the right and the left just for trying and maybe trash.

A tip is not to choose a plastic one since plastic most of the time interferes with the polarized light just like the retarder.

Post by **The_Doctor** » Mon Sep 15, 2008 3:06 pm

I don't think it will be very good. As soon as I turn my head left or right I can see the whole screen. Seems like you have to sit perfectly still in front of it.

LukePC1 wrote:why not try it out? Just move a little with the glasses on and watching only through the black eye. As long as it stays completly black you have no ghosting. If you see a little light from the screen it is some ghosting.

You can also use SG. They are polarized, too. You will just have to figure out, how to turn them...