Attaining optimal display quality on high-end LED screens requires an intricate process known as point-by-point calibration, which relies upon two systems working in concert: “Control System” and “Point-by-Point Calibration System.” In this blog we’ll take an in-depth look at point-by-point calibration’s role in improving display uniformity and its benefits for uniform displays.
What Is Point-by-Point Calibration
Point-by-point correction technology can be utilized to address display inconsistencies and elevate quality. This calibration method collects brightness and chromaticity data for every sub-pixel on an LED display before providing correction coefficients back to its control system; then these coefficients drive variations within sub-pixels for improved brightness, uniformity, color fidelity.
Basic Principles of Point-by-Point Brightness Calibration
LED displays consist of pixels arrays, each composed of red, green and blue LEDs controlled by pulse width modulation from their control system. If all LEDs on a display had only minor brightness variance (an ideal scenario), point-by-point brightness calibration can provide an effective solution. Imaging an LED display using professional cameras captures its brightness and color capturing each individual LED’s brightness/color characteristics for calibration coefficient generation which are then stored and solidified into memory by its control system.
At runtime, the control system quickly multiplies each calibration coefficient with image content to achieve point-by-point brightness calibration with pulse width compression for LEDs with brightnesses exceeding its target value to produce an uniformly illuminated display.
Unfortunately, each LED lamp has not only brightness inconsistency, but also color (wavelength) inconsistency. Its color cannot be adjusted by adjusting the brightness by pulse width, so it can only be adjusted by point-by-point chromaticity. Calibration technology comes to the solution.
Chromaticity Calibration in Point by Point
Similar to brightness variations, LEDs exhibit wavelength variations which cannot be controlled with pulse width modulation alone. Point-by-point chromaticity calibration attempts to overcome this by applying principles of chromaticity compensation – for instance if one color (such as red LED) appears too intense (i.e. long wavelength), activating its red LED will simultaneously lighten green and blue LEDs depending on image capture, recognition processing and computation to create an evenly mixed appearance which appears less intense to human eyes and decrease its perceived intensity as perceived through human perception alone resulting in less intense red.
Each pixel can be assigned its own 3×3 coefficient matrix depending on its brightness and chromaticity, which when multiplied with image data will provide both brightness and chromaticity correction.
Prior to point-by-point chromaticity calibration, LED colors on display may exhibit an irregular distribution. Following calibration, all red, green, and blue LEDs tend toward converging to one small spot at once indicating how this technology has the capacity to significantly enhance color consistency.
Advantages of Chromaticity Calibration::
Higher Color and Brightness Uniformity:
Point-by-point chromaticity calibration will be helpful for producing higher color and brightness uniformity compared to brightness calibration alone, which can effectively address nonuniformity issues in terms of both colors and brightness levels.
Reduced Brightness Sacrifice:
Comparable with point-by-point brightness calibration, point-by-point chromaticity calibration incurs less of a loss in brightness; typically between 5-8 percent when compared with point-by-point brightness calibration – an advantage particularly valuable when calibrating displays with reduced brightness due to prolonged usage.
Reaching Maximum Display Quality: Using Calibration in High-Quality LED Screens
High-grade LED displays are created to offer the optimal viewing experience, necessitating careful calibration of brightness and color to achieve uniformity across their panels.
Understanding Human Perception of Brightness
Before diving in, it’s essential to gain an understanding of how human eyes perceive brightness. The relationship between LED display brightness and perceived human brightness is nonlinear – this nonlinearity can be represented using the Gamma curve which shows changes in actual brightness don’t correspond with changes in perceived brightness directly.
Reduced brightness from 1000nit LED display to 500nit may result in an effective 50% drop, yet human eyes perceive only about 73% reduction; the nonlinear relationship seen here is represented by the Gamma Curve which emphasizes human subjectivity regarding brightness perceptions.
Explore Color Perception Strategies Here
Let’s now investigate human color perception. The CIE color chart serves to represent colors with coordinates or wavelengths; human eyes have an inherent tolerance for any visual perceptible color difference (Euv). When Euv is below 3, any difference considered minimal while exceeding 6 indicates significant distinction.
Even variations as minor as 2-3 nanometers in wavelength can be perceived by humans; though their perception can depend on color perception. Sensitivity to wavelength variations varies with each color.
LED displays must take into account various aspects of brightness and color perception to maintain consistent visuals, so their differences in brightness or hue must fall below imperceptibility thresholds to provide optimal visual consistency. Packaging components play a pivotal role in maintaining display uniformity.
Select Components for LED Displays
Selecting LED packaging components with specific brightness and wavelength ranges becomes essential during production of LED displays, to achieve optimal results. Select components with narrow brightness ranges (10%-20%) as well as wavelength ranges within 3 nanometers to ensure high levels of display consistency and achieve the best results.
However, LED displays typically use components with wider brightness and wavelength ranges than anticipated, potentially leading to perceptible differences in both brightness and color. Furthermore, COB packaging–while providing control of incoming brightness and wavelength levels–may introduce inconsistencies between displays’ output brightness levels and color accuracy.
Human perception of LED brightness changes follows an unpredictable nonlinear gamma curve and color sensitivity differs across wavelengths. Achieve a high-quality display requires meticulous calibration in order to control brightness and color differences within imperceptible ranges; selecting quality components as well as employing point-by-point correction technology further ensure a superior visual experience for viewers.