Posts Tagged ‘light polarization’
So we’re on for our second part exploring the three dimensional dreams of stereoscopy. Thank you for the feedbacks on the first part. Let’s dive into our subject.
Strange and new goggles
There are lots of different ways to get rid of the annoying color loss of the anaglyphs. One smart way is to pick 6 colors instead of 2: 2 shades of red (R1 & R2), 2 shades of green (G1 & G2) and two shades of blue (B1 & B2), that are different enough so that a filter that filters one does not filter the other. That way, we can translate our left image in R1G1B1 and the right image in R2G2B2, and then, we have our 3 dimensions with slightly no color loss.
But once we quit the Anaglyph system; there are a few techniques that are worth seeing. And to begin with, light polarization. You might know that light is the effect of electromagnetic waves. Or maybe you don’t know what electromagnetic waves are, and that’s not a problem, because you won’t need specific knowledge about it. All you need to know is those 3 facts: it oscillates (like the waves in the sea), we do know how to build filters (polarizing filters) to suppress the oscillations in specific directions, and when all the oscillation is suppressed, we don’t see anything. So here’s the plan: First, we take 2 video projectors, and they project the 2 films (left eyed and right eyed) on the same spot. One is polarized along a direction (let’s say horizontal), and the other one is polarized along a perpendicular direction (let’s say vertical). Then you wear specific glasses that have a horizontal filter or the right eye, and a vertical filter on the left eye. The horizontal filtered film can pass an horizontal filter again, so your right eye can see it, but when it comes to the vertical filter, it can’t pass through, because it would suppress all the oscillations. Thus, your right eye can only see the right eyed film and your left eye the left eyed one.
We can take this technique to a higher level : if you tilt your head 90°, your vertical filter becomes horizontal and vice versa, so instead of vertical and horizontal filters, we can use circular filters: one that turns clockwise, and the other counterclockwise. That way, even if you’re upside down, you can still see the right image. Keeping on getting better and better, video projectors (especially for cinema) are quite expansive, so there is a method to do it with only one projector : using a modulator that can polarize alternatively clockwise and counterclockwise give an electrical input. We just have to create alternative images from the left film with one polarization and the right film with the other polarization, and oscillate quickly between the images. And that’s how James Cameron’s Avatar works (see Real ID Cinema).
And at home ?
If you keep the “alternate the left and right image at high frequency” side and replace the polarization with electrostatic glasses that can cover alternatively one eye and the other, you get a good and simple way to have stereoscopy at home, given you have those glasses (let’s say Nvidia 3D Vision, 200$), a high frequency screen (at least 120 Hz if you want a neat image, keep in mind that it will be divided by 2) and you can have 3D at home and enjoy active stereoscopy!
Another solution is called auto-stereoscopy. Do you remember those cool mouse pads and fridge magnets that were so cool in the 90’s, there were 2 images on them, and depending on the direction you would watch, you would see one image or the other one. Imagine the same system mounted on a screen. Using lens, and splitting the screen into tiny vertical zones, we can make it so that if you’re right in front of the screen at the right distance, your left eye and right eye see different images. That way, we can throw the 2 films to the right eye. You want to try this out ? Check out the numerous Youtube video about the Nintendo 3DS announced at E3 2010 recently.