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DLP, Checkerboard, and 3D

post #1 of 21
Thread Starter 
I have not been able to find an adequate layman's explanation for how DLP uses the checkerboard format to display images in both 2D and 3D, so I decided to try and explain it myself.

Please feel free to read and comment.

Attachment 228720

EDIT: Further discussion here http://www.avsforum.com/avs-vb/showt...9#post20625259

 

DLP, checkerboard, and 3D.pdf 165.0263671875k . file
post #2 of 21
Dig it. Best introductory-level treatment I've seen to date. Charts, and their explanations, are what make it work.
post #3 of 21
Nice job on the write up!
post #4 of 21
post #5 of 21
Thread Starter 
Quote:
Originally Posted by Bruce M. View Post

Dig it. Best introductory-level treatment I've seen to date. Charts, and their explanations, are what make it work.

Quote:
Originally Posted by taz291819 View Post

Nice job on the write up!



Thanks for the comments.

Yes. I drew from all of those sources. I've found that some people read those and still do not understand how it works. These are the people who swear checkerboard is 960 x 1080 or 1920 x 540 per eye. They still think in square pixels, and not diamonds.
post #6 of 21
I disagree with the following staatement.

HP’s “Wobulation” or TI’s “SmoothPicture” is the process of shifting the light from the DLP mirrors from the locations shown as purple squares
(L), to the locations shown as orange squares (R) in figure a. This happens very fast, and the combined sub-frames form one complete video
frame.


A 3D video frame can not contain both the left eye and right eye images simultanously on a DLP screen.

Each time a "wobble" occurs(every 120th of a second) the video frame changes from left to right or right to left and the white DLP Linik white flash is displayed on the screen to control the active shutter glasses lenses.
post #7 of 21
Thread Starter 
Quote:
Originally Posted by walford View Post

I disagree with the following staatement.

HP’s “Wobulation” or TI’s “SmoothPicture” is the process of shifting the light from the DLP mirrors from the locations shown as purple squares
(L), to the locations shown as orange squares (R) in figure a. This happens very fast, and the combined sub-frames form one complete video
frame.

A 3D video frame can not contain both the left eye and right eye images simultanously.

Each time a "wobble" occurs(every 120th of a second) the video frame changes from left to right or right to left and the white DLP Linik white flash is displayed on the screen to control the active shutter glasses lenses.

The quoted passage was describing how a DMD chip paints a 2D frame of video. DLPs use the checkerboard format to use half the number of mirrors in order to render all of the number of pixels. And 120th of a second is very fast to me.

From the preceding paragraph
Quote:
Figure a. is a representation of the left and right sub-frame pixels in a DLP (checkerboard) 2D input.
post #8 of 21
I agree 120th of a second is fast and it is the minimum refresh rate used by all 3D flat panel TVs in order to display 1080p per eye 3D content Many LCD/LED 3D TVs use as 240 fps refresh rate and some others even have 480 fps refresh rate.
post #9 of 21
Thread Starter 
Quote:
Originally Posted by walford View Post

I agree 120th of a second is fast and it is the minimum refresh rate used by all 3D flat panel TVs in order to display 1080p per eye 3D content Many LCD/LED 3D TVs use as 240 fps refresh rate and some others even have 480 fps refresh rate.


I don't see the point of your post. This thread is not about flat panel displays nor their refresh rates.
post #10 of 21
DLP refresh rates cannot be compared to LCD or Plasma since by using mirrors their is no decay time so ghosting does not become a problem. The quality of a DLP display is actually quite amazing. I believe for digital projection DLP is the preferred method.
post #11 of 21
I agree that no ghosting or video crosstalk can occur on the DLP screen due to the speed of the DMD chip. However ghosting or crosstalk can occure if the active shutter glasses used do not respond fast enough.
post #12 of 21
Thread Starter 
Can we get back on topic, please?

Increasing refresh rate to compensate for flat panel display flaws and cheaply made 3D glasses have little if anything to do with DLP technology.
post #13 of 21
its amazing that 07 3d tv tech smokes 2011 3d tv tech
post #14 of 21
Thread Starter 
+1
post #15 of 21
Quote:
Originally Posted by walford View Post

I agree that no ghosting or video crosstalk can occur on the DLP screen due to the speed of the DMD chip. However ghosting or crosstalk can occure if the active shutter glasses used do not respond fast enough.

If using DLP-Link active shutter glasses that blank out the sync flash at the beginning of each frame (left and right eye) then it seems to me there shouldn't be any ghosting or crosstalk due to the shutters not being fast enough. If that were the case you would still see the lighter image due to the sync flash, like you do when using IR sync glasses with DLP-link active.
post #16 of 21
DLP link glasses do not blank out the white flash they receive and process the white flash and if they do not respond and change shutters fast enough they can cause video cross talk.
post #17 of 21
Thread Starter 
We know that the DLP-Link glasses receive the DLP-Link flash.

The flash creates a "wash-out" or "tinted black" effect in the picture seen by the naked eye and the effect is still visible with IR glasses.

That effect is not seen through the DLP-Link glasses (lens timing?), so they effectively block it from view.
post #18 of 21
I'm curious as to what the "tinted blacK' is supposed to look like.
Do you have an example?
I've heard of the "red tint", and seen it, but I do not know what tinted black is supposed to look like.
post #19 of 21
It sounds like to me that they are implementing 3D much like doing an IVTC on interlaced HD material to get a progressive scanned picture.

It's definitely not quarter, or even half resolution. In fact, unless LCD magically has more pixels than, 1080p it seems it should be on par, assuming your glasses are good. If anything, it sounds like LCD was unable to do checkerboard because it doesn't refresh fash enough, so they had to do a dual view approach (not to mention forcing everyone to buy new AV receivers),
post #20 of 21
Thread Starter 
Quote:
Originally Posted by hceuterpe View Post

I'm curious as to what the "tinted blacK' is supposed to look like.
Do you have an example?
I've heard of the "red tint", and seen it, but I do not know what tinted black is supposed to look like.

Same thing. I think Samsung DLPs have the red tint, my mits has a blu-green tint.
post #21 of 21
Thread Starter 
Quote:
Originally Posted by hceuterpe View Post

It sounds like to me that they are implementing 3D much like doing an IVTC on interlaced HD material to get a progressive scanned picture. ...[snip]

It's interleaved, not interlaced. Interleaving combines information from the same frame, so theres no "jaggies" or other motion artifacts.
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