Simpler than Black Data Insertion Driving Patent by LG Display

[stl8k]

Recent LGD patent for alternative to BDI/BFI...

"Referring to FIGS. 3 and 4, the temporary emission method according to an embodiment of the present disclosure may be a method proposed for enhancing a motion picture response time (MPRT) in the electroluminescence display apparatus which is a hold type apparatus. The temporary emission method may enhance the MPRT characteristic by using a driving method which is simpler than a black data insertion (BDI) method of the related art. In the BDI method, because a separate black voltage should be applied for displaying a black image subsequent to an original image in the same frame, the cost may increase and a driving scheme may be complicated. On the other hand, in the temporary emission method, because it is not needed to apply a separate black voltage, a problem caused by the BDI method may be solved. Also, in the temporary emission method, because the emission period is adjustable to be relatively long in one frame, high luminance may be realized at the low cost."

https://patents.google.com/patent/US20210398489A1/en

[thatoneguy]

This is very interesting. Sounds a lot like strobing.
I'm curious as to what Chief's thoughts on this are.

[Chief Blur Buster]

It's clever.

Simply put, it's sorta pixel-level BFI built into each pixels. While more complex than discrete full-frame BFI, it's a surprisingly simple method of per-pixel BFI.

Traditionally TFT panels had only one transistor per pixel, but this TFT has two capacitors and two transistors per pixel according to the patent, this is the pixel block diagram:

lg-automatically-resetting-bfi-pixels.png (55.91 KiB) Viewed 2418 times

This block is repeated for every single subpixel on the display:

lg-matrix.png (545.16 KiB) Viewed 2415 times

So only one voltage pulse per refresh cycle is needed -- to refresh the pixel. The transistor automatically turns off the pixel when the pixel capacitor discharges low enough. One of the capacitors is intentionally designed to have more charge than the other, and is part of how the pixel is self-resetting (produces the BFI / OFF long before the next refresh cycle).

Remeember -- modern active matrix screens are just essentially giant computer chips on glass (or even plastic, as in folding OLED phones). The screen is one big chip. Manufactured with lithography masks shining a circuit onto a large piece of specially treated motherglass. It's sort of like developing a photograph enlargement, except very exactingly precise -- these plants now cost hundreds of millions of dollars at least, and often now billions of dollars nowadays. This is true for both active matrix LCDs and active matrix OLEDs, and any ultra high resolution screen technology fabricated with lithography technique.

Even though it's only 66 million transistors for an 8K screen utilizing 2 transistors per pixel, the giantness and transparentness of the "chip" (piece of glass) makes this hugely difficult. The high clock rates required for refreshing fast (8K 120Hz = 12 billion subpixels refreshed per second) -- over long microwires that can extend over a meter -- can makes a 2-pass BFI refreshing algorithm hard to do efficiently at low MPRTs. So a 1-pass scanout makes it easier to optimize the refresh rate without sacrificing BFI and/or HDR.

Self-resetting pixels (pixels that black out sometime after the scanout pulse), eliminate the need for a traditional "OFF" pass (either frame-based or rolling-scan based):



(From Custom OLED Rolling Scan Thread)

LG patent eliminates the need for the "OFF" scan pass to black out pixels. This LG patent is essentially a self-blacking pixel. For the average layperson, the capacitor can be thought as a metaphorical BFI timer to turn off the pixel automatically, without needing a separate scan pass.

Variable MPRT effects will probably occur, with brighter colors having more motion blur than darker colors, but that's something that happened to CRTs too -- more ghosting occured with brighter colors. It's not a bad compromise, to get HDR brightness levels, while keeping low motion blur of most moderately-bright-and-dimmer colors.

Even human eyes have this effect when fast-moving bright lights go past our vision in the real world -- like darting our eyes accidentally past the sun (or a bright streetlamp at night) and the ghost trail lingers in your retinas for a while. It also hugely mitigates flicker that becomes more visible for brighter colors,

This form of BFI can also theoretically be done laglessly, with a CRT-like scanout effect, assuming this display can be scanned out in a subrefresh manner much like modern gaming LCDs can.

Kudos to LG if they can get high-Hz + HDR + low persistence working concurrently. This patent would be a movement towards this goal with simpler refreshing electronics.

Once it's a real product (could be years, or not) -- LG ought to send their prototype for a Blur Busters Approved logo!