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Discussion Starter #1
Can plasma (4-6 ms) be improved to equal the picture quality of CRT (1.6 ms) on fast moving images? Could plasmas be made with 120 Hz tech and BFI to go down to 2-3 ms or lower?
 

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Last time I checked, plasma TVs were faster than 4 ms (and that was for 2004 models).


Heck, even the upcoming Pioneer 8th gen plasma TVs already have something like 2 ms or 1 ms of response time (which is CRT-like in speed).


However, if you think want something faster than any other display tech, you could just wait for OLED TV.


With its
 

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CRTs - resposnse time is governed by phosphor decay and is ~ 1.5ms.
Plasmas - response time is governed by phosphor decay and is ~ 1.5ms.
LCDs - using overdrive can achieve response times of 2-4ms.


But!! if you use "hold time" as a measure of motion performance you get different numbers. It has been shown that hold time contributes to 70% of motion blurring in displays.


Note: Hold time is the time the pixel is "on" during each frame period of 16.7ms.

CRTs - hold time is governed by phosphor decay and is ~ 1.5ms
Plasmas - hold time is governed by PWM and is 4-6ms
LCDs - hold time is governed by "active matrix" and is equal to the refresh rate (8.3ms for 120Hz, 16.7ms for 60Hz)


This is why CRT still has an advantage over all displays.


And BTW, OLED will only have an advantage "if" it uses passive matrix. If they used "active-matrix" the motion handling will be very poor.
 

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Discussion Starter #6
Thank you xrox !!! I'm waiting for OLEDs.


On a plasma can anything be done with PWM to make it to 1.5ms?


What are active and passive matrices? Is passive matrix possible (or for that matter desirable) in LCDs?


During last CES Sony showed OLED monitors. Did they have a passive matrix inside?
 

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Quote:
Originally Posted by moreHD /forum/post/0


Thank you xrox !!! I'm waiting for OLEDs.


On a plasma can anything be done with PWM to make it to 1.5ms?


What are active and passive matrices? Is passive matrix possible (or for that matter desirable) in LCDs?


During last CES Sony showed OLED monitors. Did they have a passive matrix inside?

Something can always be done. To decrease the hold time in plasma displays they must increase luminous efficiency. Pretty much every single plasma manufacturer is researching this as it is a key enabler for 1080p, power consumption, and hold-time reduction.


Active matrix is a term used to describe the use of TFTs behind each pixel which acts as a switch to turn each pixel on and off. This allows the display to turn all pixels on all at once and "hold" them on for the entire frame period. This is done to maximize brightness.


Passive matrix does not have TFTs behind each pixel. Pixel activation occurs in a line-by-line fashion. LCDs have trouble with this because of the slow response of the crystals and very low brightness. This is why modern LCDs use active matrix.


Sony's OLED is active matrix I think. I assume this because in schematics they show "TFT substrate" which suggests active matrix.
 

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Discussion Starter #8
So, OLEDs can 'respond' very fast and have a high brightness so they don't need TFTs, so passive matrix pixel activation can occur, right?


What's that "TFT substrate" for, then? Could this be because Sony is cheating on BLUE color oled and they need to TFT it?
 

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Quote:
Originally Posted by moreHD /forum/post/0


So, OLEDs can 'respond' very fast and have a high brightness so they don't need TFTs, so passive matrix pixel activation can occur, right?


What's that "TFT substrate" for, then? Could this be because Sony is cheating on BLUE color oled and they need to TFT it?

Regarding OLEDs there are advantages and disadvantages to using TFT-(active matrix) or not using them(passive matrix):


Active matrix OLED - has high brightness with low current and long lifetimes but has hold type motion problems like LCD.


Passive matrix OLED - has high brightness with very high current and very short lifetimes but better motion handling for video.


Note: I've also heard that Passive matrix OLEDs have been used with PWM like plasma displays to reduce current and increase lifetimes. But again the thold time will be similar to plasmas


Cheers
 

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Discussion Starter #10
What is the lifespan of passive matrix-ed OLEDs? By how many percent shorter?


I just read a thread about 32" Novalux/Necsel LCD prototype with LASER backlight. Any significant improvements in response and hold times, here?


I want to learn about a display technology that could take the crown off CRT in respect to the least perceived motion blur.


xrox,

Do you possess similar data on projection tech., like DLP, LCoS, 3xLCD(better motion than direct view LCD?!) Any differences in response and hold times between 'front' and 'back' projection? Is 3-chip DLP front projection the 'fastest'? What can be the fastest?

Can LASER-'driven' TVs equal CRT-quality for fastest changes and shortest holds?
 

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Quote:
Originally Posted by moreHD /forum/post/0


What is the lifespan of passive matrix-ed OLEDs? By how many percent shorter?


I just read a thread about 32" Novalux/Necsel LCD prototype with LASER backlight. Any significant improvements in response and hold times, here?


I want to learn about a display technology that could take the crown off CRT in respect to the least perceived motion blur.


xrox,

Do you possess similar data on projection tech., like DLP, LCoS, 3xLCD(better motion than direct view LCD?!) Any differences in response and hold times between 'front' and 'back' projection? Is 3-chip DLP front projection the 'fastest'? What can be the fastest?

Can LASER-'driven' TVs equal CRT-quality for fastest changes and shortest holds?

I'll have to look up the lifetime difference but it must be an order of magnitude or more?


I don't have data on other technologies but I know DLP uses PWM like plasma so hold times will be similar and laser driven TV's hold time will depend on laser power (get a high enough brightness with a really short laser pulse)


Note: Pioneer has developed an extremely high efficiency plasma display. They claim 5 fold increase in efficiency which can translate to many things

-smaller cells (higher resolution or smaller displays)

-much shorter hold times since you need much less PWM time to achieve high brighntess.
 

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Is it the rise and fall time of the pulse that ads the extra milliseconds to the hold time? 4-6ms, minus phosphor decay time of 1.5ms is 2.5-4.5ms. What are the benefits from a hold time lower than 4ms?
 

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Quote:
Originally Posted by borf /forum/post/15642484


Less blur and lots of flicker.

A you sure about the blur part? Xrox said in another thread that "As far as human perception. It has been concluded through research that 4.17ms is near or at the threshold for perception of hold type motion blur"
 

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Quote:
Originally Posted by jonten123 /forum/post/15640625


Is it the rise and fall time of the pulse that ads the extra milliseconds to the hold time? 4-6ms, minus phosphor decay time of 1.5ms is 2.5-4.5ms. What are the benefits from a hold time lower than 4ms?

The 4-6ms number comes from the idea of "effective" duty cycle. In a 16.7ms frame period the brightest pulses (subfields) are all at the end of the frame period.


For example see this graphic I made describing the flicker perception at 48Hz for CRT, PDP, and LCD. The "effective" duty cycle is the dotted line. Effective duty cycle is what determines our percieved hold time in these examples. Note, these are just totally made up graphics to explain the concept.




Note: The phosphor decay (fall time) for green phosphor in plasma is at least 8ms to 90% decay. This is the limiting factor IMO in going above 900 lines of motin resolution.
 

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Quote:
Originally Posted by jonten123 /forum/post/15642575


A you sure about the blur part? Xrox said in another thread that "As far as human perception. It has been concluded through research that 4.17ms is near or at the threshold for perception of hold type motion blur"

Actually, I can't take credit for that. I just relayed information I read from a Sony paper on LCD motin blur. Note that they are now releasing a 240Hz LCD which is 4.17ms hold time.
 

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Thanks for the explanation! I see now why increased luminus efficency can decrease the hold time. I saw that neopdp´s has the same brightness as plasmas of today but half the power consumption! I guess that means shorter pulses which equals shorter effective duty cycle or just lower drive voltage. Have the decay time of the green phosphor been improved since it where used in crt´s? What is the decay time for red and blue phosphor?

I`ve read that the panel must cycle the image several times per frame to create the shades of grey. What are subfields? Has a subpixel in the first subfield just a different colortone and brightness than in the next subfield? And when all subfields are seen together the actual frame is displayed. Why are the brightest subfields at the end of the frame period?
 

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Quote:
Originally Posted by jonten123 /forum/post/15644980


Thanks for the explanation! I see now why increased luminus efficency can decrease the hold time. I saw that neopdp´s has the same brightness as plasmas of today but half the power consumption! I guess that means shorter pulses which equals shorter effective duty cycle or just lower drive voltage.

Unknown what they did with the extra efficiency. They may keep the same pulse widths and brightness would be boosted just due to the increased efficiency (each pulse is brighter than before). Until more details come out I can only speculate.


Quote:
Originally Posted by jonten123 /forum/post/15644980


Have the decay time of the green phosphor been improved since it where used in crt´s? What is the decay time for red and blue phosphor?

Panasonic has a patent on a 8ms green phosphor. They also have hinted that the neopdpeco has 1080 lines of motion resolution due to the shorter afterglow of phosphor. Details are sketchy at the moment. Typically phosphor decay is longest for green and shortest for blue.

Quote:
Originally Posted by jonten123 /forum/post/15644980


I`ve read that the panel must cycle the image several times per frame to create the shades of grey. What are subfields? Does each subpixel in a subfield have a different color and brightness than the next subfield and when all subfields are seen together the actual frame is displayed. Why are the brightest subfields at the end of the frame period?

Subfield is an alotted time period for the pixel to emit light. In the example graphic above there are 8 subfields of increasing widths (which relate to increasing brightness). The panel then uses combinations of subfields to create the desired brightness of a pixel. In a binary subfield system the widths of the 8 subfields are as follows 1,2,4,8,16,32,64,128. Using this system there are 256 possible combinations and hence 256 gray levels. All pixels have to be emitting the same subfield at the same time (except for Pioneer).
 

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Ok, but doesn´t the the hold time decrease if some subfields aren´t being used? 11111111 should result in a 4-6ms hold time? What about 10000000? Why does the hold time vary from 4-6ms?


So a Panasonic with 100fps (European model) will actually be at 800Hz (pulses) then. Pioneer with 100fps * 14 will be at 1400Hz. Why not use that in marketing?
 
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