Electrical Notes: WORKING WITH PASSIVE 3DTV
Below, we zoom way in to the pixel level for a look...
The left and middle panels show 5 x 5 pixel blocks of the 3DTV. The left panel appears as it would through a lens of the special glasses, and the middle panel appears as it would to the naked eye. Each pixel is composed of 3 subpixels - a red, green and blue one. As would be expected due to its larger size (32" vs 23"), the 3DTV's pixels are substantially bigger than those of a typical HD monitor, and have somewhat more black "frame" area than a non 3D monitor (right panel). The .728mm row pitch in 3D mode is quite large and results in the "venetian blinds effect".
Zooming out a little and showing what the special polarizing glasses do
The red, green and blue sub-pixels can no longer be distinguished... their colors have "fused" into full color whole pixels (the colored squares).
The left lens of the glasses allows only the "A" rows to be transmitted ("B" rows appear black).
The right lens of the glasses allows only the "B" rows to be transmitted ("A" rows appear black).
These black horizontal lines that each eye sees are pretty big: .728mm apart and taking up 62% of the total image area. One needs to view such a screen from about 7 feet back in order for these to fuse with the rest of the image... at that range the pixels and lines can't be percieved and the images "smooth out".
3DTV is handed THIS via HDMI cable:
(Top / Bottom format stereo pair, 1920 x 1080 pixels)
If TV is in 2D mode, it appears as shown.
As far as the PC is concerned, the 3DTV is just like any other monitor. There is no "handshaking".
If TV is in 3D TB mode, it appears as shown at left and (magnified) at right.
To switch modes: [menu, 3D, TB]. The top / bottom pair becomes an overlayed pair. The 3DTV has no intelligence about its interpretation of the input: it simply takes the top half and considers it the left image, and the bottom half the right image.
To create 3D output on the 3DTV, the computer must first construct a properly aligned top / bottom stereo pair from the original pictures (above). This could be done manually with photoshop, with Stereo Photo Maker, or a custom application. This pair must be scaled to 1/2 height, since it will get height doubled on the output end. The PC then outputs this pair fullscreen on an HDMI cable going to the 3DTV. The 3DTV line could be considered by the PC as a primary or secondary monitor, or T'd off either of those via an "HDMI splitter".
Top / bottom pairs result in higher quality output than side by side format, since the 3DTV only has 540 rows per image anyway.
3DTVs are now available for amazingly low cost ($350 in 2012), and can easily be used as a 3D computer output devices. The tested unit is a Vizio E3D320VX, 32" diagonal, but the principles apply to similar passive 3DTVs as well.
It was relatively easy for manufacturers to make such a device because, for the most part, it's like any other flat screen: a big grid controllable pixels. The magical extra feature of passive 3DTVs is a polarizing layer which, when the special glasses are worn, blacks-out every other row. The screen can be thought of as having alternating "A" and "B" polarization rows. The left lens of the glasses only transmits the "A" rows , with "B" rows appearing black; and the right lens only transmits "B" rows, with the "A" rows appearing black.
The bottom line for the user is of such an "interlaced" display is that each eye sees an independent 1920 x 540 pixel image, which gives fairly good 3D viewing experience.
The caveat is that interlacing results in a "venetian blinds" effect, which necessitates fairly long viewing distances.
Some other observations regarding the Vizio E3D320VX passive 3DTV
- It's bulky
- remote is horrible - often skipping clicks, often doubling clicks
- remote doesn't have a 3D button, (although they had room for an Amazon button), to get into top/bottom 3D mode requires 10 clicks (or more since the clicks don't always register)
- doesn't remember its mode at powerup... to get into 3D you need to go through the menu steps each powerup
- View angle is crucial for 3D - your head must be below the top of the TV or severe ghosting occurs. Center-ish, 7 feet back, and low is the sweet-zone
- 3 people can sit in the 3D sweet-zone
- 2 pairs of supplied glasses work well
- Real3D glasses from the cinema work just as well
- Sit still! Any left-right movement while watching 3D is disturbing - causing brain confusion
- Be sure to use top/bottom format rather than left/right to gain twice the resolution
- Rolling head (tilting left or right) has no effect on 3D
- Looking at TV through mirror reverses the left-right views (a strange experience)
- When all set up correctly, and viewing properly shot and aligned content, 3D looks good
- Fantastic price
- Pretty wide bezel (1.6"), makes it awkward to create multi-monitor arrays
- I have not tried it as a TV or for movies
- Looks pretty good as a large 2D monitor (especially if you need to sit ~3' away) if the sharpening and other image tweeking is simply turned off
- Passive 3D at this resolution can't become ubiquitous for computer monitors because of the long distance requirement.