Custom OLED Rolling Scans -- Custom Built OLED Monitor

Advanced display talk, display hackers, advanced game programmers, scientists, display researchers, display manufacturers, vision researchers & Advanced Display Articles on Blur Busters. The masters on Blur Busters.
User avatar
Chief Blur Buster
Site Admin
Posts: 9060
Joined: 05 Dec 2013, 15:44
Location: Toronto / Hamilton, Ontario, Canada

Re: Custom OLED/MicroLED Rolling Scans -- Custom Built OLED/MicroLED Monitor

Post by Chief Blur Buster » 15 Jul 2020, 13:16

(continued from previous page)
Chief Blur Buster wrote:Oh, by the way, there's an important caveat when multiscanning. If you do it wrong, it will sawtooth:

(Sawtooth artifact caused by multi-scanning of the SAME refresh cycle -- more info in this thread)

To prevent sawtooth artifact problems caused by old-style multiscanning, (A) each concurrent scanout pass must be complete top-to-bottom, and (B) each individual scanouts must correspond to a complete, separate, consecutive refresh cycle (frame). To avoid the dreaded multiscan sawtooth, you must avoid multiscan of the same frame (refreshing the SAME refresh cycle in separate scanouts at the same time on different parts of the screen). Each scanout must be of separate frames.. That way, there can be safely be multiple scanouts concurrently on the same screen, with NO sawtooth artifacts at all.

Slower scanouts will have more skewing (e.g. See your computer monitor scan skewing here: ...) but this is mostly insigificant at 1/120sec scanout velocities. And we all know, that a minor skew is not nearly as noticeable as sawtooth.

Then you can 8-way multiscan the same 120Hz OLED, to achieve [email protected] with absolutely ZERO sawtoothing.
Addendum about artifact-free parallel scanouts, because some screen technologies are modular -- creating a convenient refresh rate parallelization opportunity:

Possible Application: Jumbotrons & MicroLED Displays

LED Jumbotron modules are already 600 Hz to 1920 Hz
That's the screens you see in stadiums today (as of 2019, 2020, pre-COVID). Many LED Jumbotron modules are 32x32 or 64x64 pixels in square-shaped modules. They run at a frame frequency of 60 Hz but refresh each LED 10 times, so there's a LED refresh frequency of 600 Hz. Some minor modifications in the modules allow them to run at a frame frequency matching refresh frequency = retina refresh rate JumboTrons!

MicroLED panels are similar architecture
The MicroLED panels found on LED cinema screens such as "The Wall" and other MicroLED displays are also similarly modular -- they are essentially miniaturized, higher-density versions of giant stadium LED Jumbotrons. In this COVID-pandemic, a boom of LED Jumbotrons are appearing. Now, we have UltraHFR developments -- -- which could become popular by the 2030s.

The multiscaning algorithms are perfect for this
The custom-OLED-rolling-scan algorithms I've posted in this thread is perfect for these modular LED approaches. Including the zig-zag artifact problem of concurrent multiscanning. That said, the engineering goal is that you need one unique refresh per module scanout, and each row of LED panels would need to use the algorithm that prevents sawtooth tearing artifacts from multiscanning.

That said, if there's many rows, you're going to have to stack the scanouts at a fixed velocity controlled by a LED module's individual scanout velocity. That's the unchangeable constant (if you don't want scan artifacts). For example, if the scanout is 1/1200sec (1200Hz capability), and your screen is about 32 modules tall (32 rows of LED modules), you will need to spend 32/1200sec sweeping the full screen height, while following this algorithm, to prevent sawtooth / tearing / zigzag / combing motion artifacts. You'd have 32 concurrent scanouts assigned its unique frame/refresh sweep, that transfers between those as the frame's sweep reaches the end. Your refresh rate will still be the module refresh, regardless of screen height. You won't have zigzag artifact problems with -- (just a bit of line-tilting which is not a major problem, assuming a reasonably fast global sweep, as this has existed on almost all 60Hz screens due to the slow scan).

The important thing is that your zigzag-artifact multiscan artifact is fixed with this algorithm, and the technology becomes scalable (from Jumbotrons to MicroLEDs). If your screen requires many modules in height, you may want to speed up individual-module scanout velocity, so that your total screen height is quickly scanned in one unidirectional sweep (as the individual module scanouts cascades their scanout to the next LED module).

The bottom line is that this provides a potential modular engineering path towards:
- Very scalable
- This thread is perfect for modular LED
- Retina refresh rates in modular LED (jumbotrons, MicroLED, Wall displays, etc)
- Modular LED is very friendly to this algorithm I've written in this thread
- Modular LED screens that can be a variable number of modules tall
- Could be compatible with future projectorless cinema UltraHFR screens, a perfect market for UltraHFR at

Mathematically, your scanout sweep will be [module strip count]/[scanout cycles per module], so 24 rows of 1000Hz jumbtron modules would require 24/1000th of a second for a global top-to-bottom sweep, and you would need 24 concurrent scanouts for 1000fps at 1000Hz. Or 12 concurrent scanouts (separation of scanout pixel rows would be two modules apart vertically) for 500fps at 500Hz, alls sweeping in the same direction (typically from top edge to bottom edge).
Head of Blur Busters - | | Follow @BlurBusters on Twitter

       To support Blur Busters:
       • Official List of Best Gaming Monitors
       • List of G-SYNC Monitors
       • List of FreeSync Monitors
       • List of Ultrawide Monitors

Post Reply