While the science of LED screen appearance is complex, the correction process implemented in VisionTUNE™ makes it easy to have a good looking screen!
Screen Correction Theory
LED Screen Correction Basics
The core concept of LED screen correction is straightforward: the input signal sent to each LED in the screen is adjusted to account for LED-to-LED performance variations. Dim LED screen pixels are brightened and overly bright LED pixels are dimmed to match an overall target brightness. Pixels that are too red will mix in a bit of blue and green, and pixels that are a too green mix in a bit of red and blue, and so forth, so that they all can produce the same colors.
As a result, each LED screen pixel displays the same brightness and color for the same input.
While this helps, in almost every case luminance and color non-uniformities noticeable to the human eye still remain.
The First Secret
The first secret of VisionTUNE™ correction is that the exact color and brightness of each LED in the display must be measured.
That is why a calibrated imaging colorimeter is used instead of a consumer-grade digital camera. If this data is not accurate, the display appearance will not be optimized. Technically speaking, the RGB input signal to an LED display pixel is multiplied by a correction matrix to provide a new RGB signal.
The Second Secret
The second secret of VisionTUNE is to account for human perception.
The human eye does not have a simple or uniform response to any color or image. So VisionTUNE includes a compensation for human visual perception on top of the straight mathematical calculation when remixing colors to output a balanced, accurate, and pleasing image.
A Short Summary of LED Science
Newly manufactured LEDs have natural flaws in their crystalline structure that causes variation in color and brightness. To minimize the variations when assembling LED video screens, LEDs are often purchased in binning lots that seek to minimize the variation between LEDs. While this helps, in many cases luminance and color non-uniformities still exist at a level that is noticeable to the human eye.
The Third Secret
The third secret of VisionTUNE is that many LED display manufacturers actually correct their screens as a final step before shipment. They do this to optimize screen appearance when LED binning is not enough to produce adequate uniformity.
This is good news because it usually means that the correction coefficients can be updated in the screen as the screen is used and performance declines.
Once the LED screen is installed and used, individual LEDs start losing brightness at different rates. The rate varies with physical, electrical and environmental factors, but it is inevitable. Pixel-level graininess appears in displayed images, along a shift in color (e.g., white colors tend to become pink!).
The Fourth Secret
The fourth secret of VisionTUNE is that this correction methodology can be applied to almost any LED screen on-site, in the field, where it is installed!
VisionTUNE is not a lab experiment, needing to be run in a controlled environment. It is a robust, field-proven technology that has been tested around the world for almost 10 years.
The Fifth Secret
Almost any LED display can be corrected, whether correction capabilities are built into the screen or not! For screens that do not have internal correction processing, VisionLINK™ is an external processor that adjusts the input video in real-time, making correction easy to apply to either new screens or older, legacy screens.