LED displays are widely used in commercial advertising, stage performances, and traffic guidance. As they age, color deviation becomes increasingly prominent. Automatic point-by-point correction technology, an effective solution to this persistent problem, is reshaping the visual experience of LED displays.

Analysis of the Root Causes of Color Determination

The discreteness of LED lamp beads is the primary factor. Even within the same batch of LEDs, brightness and color can still vary by ±20% and ±5nm, respectively. During display manufacturing, uneven assembly of modules and housings, as well as internal heat distribution, can interfere with light propagation and the operation of the LEDs. Over time, individual LED light decay can vary significantly, leading to rapid brightness decay and significant color drift in some LEDs. This can cause image pitting and bright/dark spots on the screen, seriously impacting the display quality.

Explaining the Principle of Automatic Point-by-Point Correction

Automatic point-by-point correction technology uses specialized cameras and spectrometers to collect brightness and color data for each pixel (or primary color sub-pixel) on the display. The camera images the screen to obtain raw pixel data, while the spectrometer precisely measures the spectral distribution at each point to determine brightness and color values. Based on this data, the system generates a correction coefficient matrix and feeds it back to the control system. The control system uses these coefficients to drive each pixel differently. For example, for LEDs with brightness above the target, the control pulse width is compressed to reduce brightness. By compensating for color mixing of the three primary colors, chromaticity deviations are adjusted to achieve precise brightness and chromaticity correction, improving brightness uniformity and color fidelity.

Technical Process Detail

1. Data Acquisition: In factory mode, a high-precision CCD-based planar luminance/chromaticity distribution measurement instrument can be used to collect data point by point on modules and cabinets. The single-machine multi-probe design improves efficiency. In field mode, an industrial camera, mounted on a stable tripod, selects the optimal viewing area and captures data across the entire screen according to a pre-set grid, ensuring accurate data that matches the actual viewing angle.

1. Correction Data Generation: The collected raw data requires correction processing. For example, during factory cabinet calibration, the data may be smaller due to light interference from edge lights. In field calibration, systematic errors due to varying viewing angles may occur, requiring correction in both cases. Setting calibration target values is crucial. It's crucial to balance brightness, color gamut, and uniformity. Based on statistical analysis of collected data, appropriate brightness and chromaticity target values are set, laying the foundation for subsequent calibration data calculation.

1. Calibration Data Application: Currently, drive control is primarily achieved through pulse width adjustment. The control system reads the calibration coefficient matrix and, when displaying the image, performs high-speed multiplication of each pixel's image data with the coefficient matrix, adjusting pixel brightness and chromaticity in real time to produce a calibrated image. Some older screens can be calibrated at the signal source level using a front-end video processor. While this may result in grayscale loss and other issues, it can improve display quality.

Highlighting the Technical Advantages

Applying automatic point-by-point calibration technology significantly improves the uniformity of LED screens, resulting in more accurate colors and a more detailed image. After calibration, the uniformity of a large screen in a commercial plaza increased from 60% to 95%, extending audience retention by 20%. This technology also extends the display's "eye-pleasing lifespan" and reduces replacement costs. A screen that exhibited noticeable color deviation after 10,000 hours of operation can significantly regain its commercial value after calibration, reducing resource waste. Automatic point-by-point correction technology provides a systematic solution to the color difference problem of LED displays, resolving the problem at its root, improving visual quality, and promoting the continued and efficient application of LED displays in various fields.