Complete 3D TV technical guide

vickybat

I am the night...I am...
Okay guys I had planned a compilation of 3d technology used in current displays, how its differs from cinema 3d and its negative effects on us. After doing extensive reading from various sources, I finally decided to put everything into place.
It all happened when me, our forum member cilus and my brother went to Orissa’s biggest fair known as baliyatra and saw a demo of both active 3d and passive 3d. I will extensively discuss those elements in detail. It’s a lengthy article so have patience and read.
Before starting, let me provide a few prerequisites such as IPS panel technology and how 3d works so that it becomes easier to read further and comprehend. I decided to include ips because its becoming the panel of choice over traditional VA and TN panels. Even Samsung has gone far enough to introduce SUPER –PLS which is based on ips and Samsung claims it to be an evolution of ips.
IPS – Now we all know that IPS stands for in plane switching. It was developed by hitachi limited in 1996 to cope with poor viewing angles and colour reproduction problems of TN panels. The difference here is that in IPS panels, the liquid crystal molecules move parallel to a plane rather than perpendicular.When this happens , the liquid crystal shapes are same i.e horizontal and parallel to the plane. So it appears same in any viewing angle.
This actually changes the light scattering matrix in the molecules resulting in wide viewing angles and better colour reproduction.
The following screenshot will help visualize better:

r18KM.jpg


Current adopters of IPS panels are hitachi,Panasonic and lg. Panasonic is actually one of the leading manufacturer of ips panels followed by lg.
Okay now since we are done with an important panel type, lets move on to 3d….
Stereoscopic 3D- Stereoscopy is an illusion created by the brain in seeing depth. This illusion incurs when two images from an object converge at the same focal point in our eyes. The brain then mixes both images to create a 3d image of that object.
When we see distant objects , they appear flat. That’s because rays of light coming from that object are parallel. The farther it is the ray coming to the left eye is parallel to the ray coming to the right eye. As it comes closer and closer, the rays of light seem to converge. Our eyes shift focus to adjust and we see more detail of that object including depth or in other words, how far the object is from us. If our eyes converge quite a bit, the object is much closer to us.
This very phenomenon is used in 3d displays and devices. By showing two images, in a different location, we can trick the brain to think that the object has depth. But the convergence and focal points won’t match with that of a real object. So what happens here is we use special glasses to block light from 1st image and allow light from the 2nd image and vice-versa at a fast pace. These two images of the object must have different orientations.
Doing so fools the brain to think that the light from the object in the screen converge at a point which is different from focal point because the focus is on the tv screen thus giving the illusion of depth and we can view the object in all 3 dimensions. Check the following illustration for a brief idea:

g6LuP.jpg


Now we venture into 3d’s real implementations in modern world. I will skip the anaglyph red and blue glass technology as its obsolete. Still it can be viewed in the above pictorial representation.
There are two methods that are used currently to view 3d content on displays and cinemas. They are active 3d and passive 3d. Though cinema’s use passive 3d or REAL D 3D only, the use of passive glasses have moved on to commercial displays intended for personal use. Remember that the older anaglyphic glasses were also passive but current ones are different because they use polarization technique which were not used in earlier passive glasses. Now lets venture a bit deeper shall we :

Active 3d- Active 3d is the most common and widely used 3d in commercial displays and promoted by brands like Sony, Panasonic and Samsung. They get the name active due to the glasses they support. Basically the glasses here are termed as active and not the panel. Active 3d glasses are nothing but liquid crystal displays acting as the lens of the glasses. These have a shutter mechanism that blocks light source making them opaque in one instance and transparent in the other. Active glasses have their own energy source in form of a battery from which the name active comes in.
The display running 3d content has two images with a slightly different orientation with respect to each other. Lets consider the left image as img1 and right image as img 2. Light from img1 falls on the left lens and right lens. But at this instance , the right lens turns black or simply turns opaque. Therefore only the left eye sees img1. Similarly for img 2, the left lens turns opaque and only the right eye sees the respective image. This switching technique happens at a very fast rate at around 480 times a second and the brain merges the two images by a process called binocular fusion. This creates an illusion of depth depending on the extremity of the images known as interoccular difference which is directly proportional to binocular fusion.
Now the data has to be synced between the tv screen and the glasses so that proper switching take place. This is done by infrared or Bluetooth connectivity between the glasses and the display.
Active 3d delivers 3d content in the highest resolution supported by the native display. If you are watching 1080p 3d , then the end resolution will also stay the same without any loss of clarity. But active 3d has problems of its own and the most important one is “flickering”. Though the shutter mechanism in the glasses switch at a fast rate, most of the times the wearer experiences screen flicker of alternate black and white lines. This can be annoying and in the same time have adverse effects on the brain and its perception capability. Long hours of active 3d viewing will bring health problems.
Besides this , the shutter glasses are very expensive and if a big family is viewing an active 3d content in the same living room, it becomes an expensive affair to arrange enough active shutter glasses for everybody. The pic below shows an active shutter glass:

SymBm.png


Passive3d –
Passive 3d has been around for quite sometime. In cinema’s or movie theaters who provide 3d content use this type of 3d. Passive 3d for commercial displays is developed by LG. Here, all the 3d technology is given to the display rather than the glasses (in simple layman’s terms). The main objective of passive 3d is to do away with the general problems that active 3d faces which is flickering.
Passive 3d’s are completely flicker free and provide a neutral 3d viewing experience. So how does it work? We will discuss that in the following:
Passive 3d employs a property of light known as polarization which is a property of a wave that defines the orientation of oscillations. Two types of polarization are employed in passive 3d which are linear polarization and circular polarization. The latter is used now in commercial displays.

Linear polarization- In linear polarization, the light wave, after polarization will have two orthogonal (perpendicular) components in phase. Therefore the resultant vector tip will trace a path similar to a single line. Hence its called as linear polarization.

vxffW.png




Circular Polarization- In circular polarization, the light wave, after polarization will have two orthogonal (perpendicular) components out of phase by 90 degrees. Therefore the resultant vector tip will trace a circle in the plane. Hence its called as circular polarization.
m5tbc.png

Conversion of linear polarization to circular polarization : Linearly polarized light is converted to circularly polarized light by slowing one component of the field. Effectively, the light is given a twist. This is achieved by using a material that transmits light at different speeds depending on its polarity. In the diagram below, we can see a linearly polarized light wave (simple blue wave entering at left) oriented at 45 degrees to the system. Projected onto the vertical and horizontal planes are the vertical and horizontal components of that wave (equal and in phase). When that wave passes through the material, the vertical component is slowed down so that it is out of phase with the horizontal component. When it is a quarter wavelength slower, the resulting wave is helical. To an observer receiving the circularly polarized light, the electric field of that light will appear to rotate rather than just bob up and down. Notice how the dark red horizontal component passes through without change but how the dark blue vertical component is held back. The diagram is a very very simplified version.

lpWZx.jpg


Now these two techniques are employed onto the 3d display and the passive glassesof a passive 3d setup. We will discuss circular polarization technique for 3d as linear ones are obsolete now
Here’s how:
Working:- Passive displays have a film over its panel known as FPR or film patterned retarder. This consists of several strips which perfectly align with the vertical lines of the display. Each strip of the FPR is actually a polarizer which circularly polarizes the light ( from linear to circular). Check below to see an illustration of passive glasses:
7Ttm0.jpg

Unlike active 3d, passive 3d displays send both the images superimposed at the same time. However, the vertical resolution of each frame is split into alternating lines. So, the first line will display the first line of the left image, the second line will show the first line of the second image, the third line will show the second line of the left image etc. So the left lines are left circularly polarized and right lines are right circularly polarized. Now both these polarized lights falls on the user’s glasses at once.
The passive glasses have a pair of analyzing filters a.k.a circular polarizers mounted in reverse of opposite handedness. Light that is left circularly polarized is blocked by the right analyzer and vice versa. The analyzing filters are made up of a combination of a quarter wave plate(QWP) and a linear polarizing filter. The QWP converts circular polarization into linear polarization whereas the linear polarizing filter will allow resultant wave to pass depending on its angle and handedness (left or right). The illustration below shows the working of a left handedness analyzer.

3vFbY.png


Thus each eye gets one image at an instance but the brain superimposes them into a resulting 3d image. The concept is similar to active stereoscopy albeit with a different technique employed.
But passive 3d incorporating FPR’S have a small demerit. A passive TV halves the vertical resolution to 540 lines because they are alternated with the lines from both images.
So each eye is seeing a 1920 X 540 picture. However, because both eyes are seeing a different 540 line picture, the sum is 1080 lines (the brain is said to interpret the combined image as a 1080 line picture). Thus we can safely say that So each eye is seeing a 1920 X 540 picture. However, because both eyes are seeing a different image which the brain combines, passive tv’s are fullhd. The much brighter side is that they completely do away with the flickering issues of active 3d panels.

Okay guys that’s more like it. There are other 3d techs like parallex barrier and lenticular displays which I have purposely left out as they are not so mainstream now. Planning to add them in the very near future. Please post your valuable comments for further improvements on this article.:)
 
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OP
vickybat

vickybat

I am the night...I am...
I have brought these nvidia glasses NVIDIA 3D Vision Discover to watch movies in 3D. Though it shows the 3D depth but i lost almost all colour.....

Those are anaglyph glasses and only allow cyan and red light to pass through. That's why you lost all colour. Though passive, these don't have polarizing filters.

you deserve a rep for this.very simple and nice guide.i enjoyed it.

Thanks mate.:) I appreciate the fact that you enjoyed it. Means a lot to me.
 
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clmlbx

Technomancer
Nice informative post.. I can say that in my city at least Inox uses passive 3D and PVR uses Active 3D.

I have not read whole article thoroughly but it says Passive 3D is better then Active 3d.. But some how I felt Active 3D to give best 3D effect then Passive 3D.

well but very informative post nice share. already Knew most of it.
 

ico

Super Moderator
Staff member
nice guide. ;) From what I've tried out, I prefer LG's Passive 3D over Sony/Samsung's Active 3D. Reasons are simple, it worked better for me, glasses were light and no flickering. I dislike 3D altogether though.

just a small suggestion, move the images from Tinypic to www.imgur.com. Tinypic tends to delete images quickly. :)
 
OP
vickybat

vickybat

I am the night...I am...
@ asingh ,climbx,ico
Thanks a lot guys. I really appreciate your valuable comments and i'm glad you all liked it :)

@ico

Thanks for the suggestion buddy:). I will move all images to imgur. Completely agree with your comment there. Cilus and i both checked LG's cinema 3d (passive) and other actives like sony, toshiba and samsung. LG was much better with zero flickering. The experience was pleasant and i can say that a person can view passive 3d for relative long hours without any problems.

The exact model was LG Lw5700 CINEMA3D. Its 42 inches, has led backlighting, ips panel and locally retailed @ 74k. I will post some video reviews of lg passive 3d displays here.

All images moved from tinypic to imgur :)
 
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Alok

Adventurer
Very nice Article . Informative.:thumbs:

there should be guide for

"How to Start 3d gaming"

i know these are expensive but i want to play some games in 3d. Please provide information about best gadgets and everything to start 3d gaming.
 

Mango

Right off the assembly line
Guyes can any one post some of active 3D Movies ? Please i want to try on my Sony bravia EX72
 

ham_007

Broken In
Guyes can any one post some of active 3D Movies ? Please i want to try on my Sony bravia EX72

Did u mean SBS (side by side) format???

There is no such thing like 3d Active movies!!:lol: its a technology made for glasses to watch movies in 3D :wink:
 

raghupratap

Broken In
Guyes can any one post some of active 3D Movies ? Please i want to try on my Sony bravia EX72

There is nothing like active or passive 3D movies as such. The terms "Active" and "Passive" 3D rather refer to the choice of technology that the 3D TV uses to render a 3D picture. Any 3D movie can be watched using any of the two techs.

Original 3D movies (like Avatar) look and feel much better than movies "3Dfied" later - in the lab.
 
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Jitendra Singh

Broken In
I agree with you as well. Although 3D is not really a necessity even or me, the passive 3D on LG TV's wouldn't hurt if and when you ever feel like watching 3D at home.
 

ashutosh_jain

Broken In
A huge round applause for you my good man. I have been stuck in a rut between understanding both active and passive 3D technologies. Now this guide will serve as my sacred book to decide whether my next TV will be LG or Sony!
 

Jitendra Singh

Broken In
Thanks vickybat, for this comprehensive 3D TV technical guide. Will it be too much to ask for a comprehensive 3D TV buying guide - with special focus on pros and cons of passive 3D TVs vs. active 3D TVs. Also, which are the best 3D TV brands - LG 3D TV, Sony, Samsung etc?
 
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