“why aren’t both beams affecting each other? Don’t the waves add together? Wouldn’t two spiraling lights moving together add up as it is?”

The left and right frames happen one after the other remember. So they are separated in time and would not interact with each other (as it happens they wouldn’t interact with each other anyway cos that’s not how light works – waves belonging to different photons – different packets of light – ignore each other).

What’s the point of circularly polarising? First a little bit more clearing up on what happens. Think about only the left hand lens for now – The clockwise and anticlockwise lights hits the quarter wave plate first. They are both tuned into linear polarised light by this plate. The difference is that the clockwise light becomes linearly polarised in the up-down direction whereas the anticlockwise light becomes linearly polarised in the left-right direction. You can now use a linear filter to block out the one you don’t want to reach the viewers eye.

The benefit really is all to do with head tilting. The image doesn’t darken when tilting your head in the circular set up. With the linear-only set up tilting your head causes a bit of the left image to get into your right eye and vice-versa. It really spoils the 3D I think.

I think it’s GREAT that you reverse engineered 3D for your self before reading my post. Excellent.

I did suggest a segment on 3D for Blue Peter. It could happen!

“why aren’t both beams affecting each other? Don’t the waves add together? Wouldn’t two spiraling lights moving together add up as it is?”

The left and right frames happen one after the other remember. So they are separated in time and would not interact with each other (as it happens they wouldn’t interact with each other anyway cos that’s not how light works – waves belonging to different photons – different packets of light – ignore each other).

What’s the point of circularly polarising? First a little bit more clearing up on what happens. Think about only the left hand lens for now – The clockwise and anticlockwise lights hits the quarter wave plate first. They are both tuned into linear polarised light by this plate. The difference is that the clockwise light becomes linearly polarised in the up-down direction whereas the anticlockwise light becomes linearly polarised in the left-right direction. You can now use a linear filter to block out the one you don’t want to reach the viewers eye.

The benefit really is all to do with head tilting. The image doesn’t darken when tilting your head in the circular set up. With the linear-only set up tilting your head causes a bit of the left image to get into your right eye and vice-versa. It really spoils the 3D I think.

I think it’s GREAT that you reverse engineered 3D for your self before reading my post. Excellent.

I did suggest a segment on 3D for Blue Peter. It could happen!

My buddy built me ye olde Spectrum computer console out of the blue yesterday (I mean who does random acts of kindness like that? Just fab!) and it got me to thinking…. “waaaait…. speaking of home projects! THE THREEDEE!” So I have returned once again to perplex and confuse!

If both glasses’ lenses are the same crystalline material with no variation, then both light sources probably go through the same crystal inside the projector to start with… now what I don’t understand about that is if both lights travel through the same crystal then why aren’t both beams affecting each other? Don’t the waves add together? Wouldn’t two spiraling lights moving together add up as it is?

I still don’t get the POINT of polarising circularly. Maybe if I explain to you my problem with what you are telling me you will see where I’m slipping up.

Let me copy and paste this sentence you wrote about the glasses: “without the second layer blocking one or the other you’d be getting both images in both eyes.”

If both quarter wave plate layers on each eye are converting the exact same information as you suggest, and without the horizontal and vertical filters behind them you see the same thing with both eyes, to me it sounds utterly pointless. It may as well be just a plain horizontal or linear filter if the corkscrewing light is interpreted the same by both wave plates on the eyes. If however each corkscrew were interpreted differently by different eye lenses I see no need for the linear conversion as using that alone would have differentiated the eyes from each other. Do you follow my confusion here? I’m not sure how well I am articulating my thoughts (a bit sleepy).

From what you are saying I conclude that the use of circularly polarised light is purely for the glasses to work better when tilting your head. However, if one image no longer creeps into the other eye when tilting, then the alternative can only be that you start losing vision in your eyes as you tilt your head, thus gradually getting darker, am I right? Now is the complete loss of vision that much better than ghosting and worth all the extra cost of these quarter plate projectors in the cinemas?

Ah! Am a bit depressed reading your other post. You see, one night my friend sent me an e-mail asking: “how do you make animation into 3D”, I was just typing back to him something along the lines of “why in the world do you think I would know that???” when I stopped and suddenly had a thought, DO I know? Maybe I can work it out… I used to make those Magic Eye pictures for fun so started my theories from there and stayed up all night experimenting with my camera and overlaying displaced pictures in two different colours, in effect reverse engineering it for myself. I was SO excited when I worked out how to make animation into 3D on my own you have no idea! I felt how the original creators must have felt, EUREKA! But now, I see, I could have just read it all on your site in 5 mins boooo…….

Oh yeah I will absolutely upload pics of my creation if I build my own set up! Just need to find the time.. and space… but there is no way I won’t at least attempt it at some point!

By the way, I’ve just taken a better look around your site and had a *headdesk* moment when I saw that you are Blue Peter’s “Science Guy”. Figures, of course I would need someone to explain things to me in a child friendly simple way ha ha! *Sigh* I think you should definitely recommend this as a “make” by the way! “Hey kids! Build your own 3D cinema projector!” Well if that particular pitch flies with the producers I’ll certainly tune in! (Special props if we can make one cheaply out of household items!)

PS: Not really related but oh so cool: http://www.moillusions.com/2010/02/neil-dawsons-horizons.html

My buddy built me ye olde Spectrum computer console out of the blue yesterday (I mean who does random acts of kindness like that? Just fab!) and it got me to thinking…. “waaaait…. speaking of home projects! THE THREEDEE!” So I have returned once again to perplex and confuse!

If both glasses’ lenses are the same crystalline material with no variation, then both light sources probably go through the same crystal inside the projector to start with… now what I don’t understand about that is if both lights travel through the same crystal then why aren’t both beams affecting each other? Don’t the waves add together? Wouldn’t two spiraling lights moving together add up as it is?

I still don’t get the POINT of polarising circularly. Maybe if I explain to you my problem with what you are telling me you will see where I’m slipping up.

Let me copy and paste this sentence you wrote about the glasses: “without the second layer blocking one or the other you’d be getting both images in both eyes.”

If both quarter wave plate layers on each eye are converting the exact same information as you suggest, and without the horizontal and vertical filters behind them you see the same thing with both eyes, to me it sounds utterly pointless. It may as well be just a plain horizontal or linear filter if the corkscrewing light is interpreted the same by both wave plates on the eyes. If however each corkscrew were interpreted differently by different eye lenses I see no need for the linear conversion as using that alone would have differentiated the eyes from each other. Do you follow my confusion here? I’m not sure how well I am articulating my thoughts (a bit sleepy).

From what you are saying I conclude that the use of circularly polarised light is purely for the glasses to work better when tilting your head. However, if one image no longer creeps into the other eye when tilting, then the alternative can only be that you start losing vision in your eyes as you tilt your head, thus gradually getting darker, am I right? Now is the complete loss of vision that much better than ghosting and worth all the extra cost of these quarter plate projectors in the cinemas?

Ah! Am a bit depressed reading your other post. You see, one night my friend sent me an e-mail asking: “how do you make animation into 3D”, I was just typing back to him something along the lines of “why in the world do you think I would know that???” when I stopped and suddenly had a thought, DO I know? Maybe I can work it out… I used to make those Magic Eye pictures for fun so started my theories from there and stayed up all night experimenting with my camera and overlaying displaced pictures in two different colours, in effect reverse engineering it for myself. I was SO excited when I worked out how to make animation into 3D on my own you have no idea! I felt how the original creators must have felt, EUREKA! But now, I see, I could have just read it all on your site in 5 mins boooo…….

Oh yeah I will absolutely upload pics of my creation if I build my own set up! Just need to find the time.. and space… but there is no way I won’t at least attempt it at some point!

By the way, I’ve just taken a better look around your site and had a *headdesk* moment when I saw that you are Blue Peter’s “Science Guy”. Figures, of course I would need someone to explain things to me in a child friendly simple way ha ha! *Sigh* I think you should definitely recommend this as a “make” by the way! “Hey kids! Build your own 3D cinema projector!” Well if that particular pitch flies with the producers I’ll certainly tune in! (Special props if we can make one cheaply out of household items!)

PS: Not really related but oh so cool: http://www.moillusions.com/2010/02/neil-dawsons-horizons.html