First, point-by-point correction technology concept
The current status of LED chip production process determines that even in the same batch of LED chips, the inter-individual luminous intensity and the dominant wavelength still have considerable differences. For LED display applications, this difference will seriously affect the display quality. It is necessary to first classify and filter the indicators such as luminosity, chromaticity and electrical parameters by spectroscopic color separation before they can be applied to the same display.
However, the method of splitting and color separation is used to solve the problem of inconsistent chromaticity of individual chips. Due to the lack of precision, the influence of subsequent process flow, and the inconsistent light decay of the aging process, the perfect picture quality cannot be achieved. In addition, the display screen that has been used for a period of time will also show a drop in quality due to inconsistencies such as light decay, and a “flower screen†will appear, which is also beyond the wavelength separation.
Therefore, the industry is trying to solve the problem by using the last driver of the difference in LED lighting points. This is point-by-point correction.
In the late 1990s, there was a theoretical prototype of point-by-point correction at home and abroad, and the practical exploration of this technology was initiated. However, due to the lack of applicable universal data collection tools and technical barriers, the research of this technology has been discontinuous and unsystematic for a long time, and it lacks a communication state. The point-by-point correction also lacks a recognized definition.
At present, a more reasonable definition is: point-by-point correction, that is, by collecting the luminance (and chrominance) data of each lamp dot area on the LED screen, and obtaining a correction coefficient for each lamp point (or for each The coefficient matrix of the pixel is fed back to the control system of the display screen, and the control system applies the correction coefficient to realize the differential driving of each lamp point, thereby greatly improving the pixel brightness (chroma) uniformity of the display screen.
Second, point-by-point correction technology composition
As can be seen from the above definition, the point-by-point correction technique can be broken down into the following four parts:
1. Raw data collection;
2. Correction data generation;
3. Drive control;
4. The combination of the acquisition system and the control system;
The following four aspects are analyzed and elaborated separately.
2.1 Raw data collection
Raw data collection is the first step in point-by-point correction. It is the most basic step and the slowest and most difficult step to develop. According to the collection parameters, it can be divided into brightness data and chrominance data; according to the collection object, it can be divided into module level acquisition, box level acquisition and full screen sub-area collection; according to the collection environment, it can be divided into factory mode collection. And field mode acquisition;
From the perspective of the collected technical routes and tools, it can be roughly divided into the following directions:
1. Mechanical device + photometric probe: The mechanical transducer is used to control the photometric probe to collect the number of each lamp point one by one. In the early experimental installations, the screen was placed perpendicular to the ground, and the point-and-point measurement was performed by moving the brightness meter with a rack equally spaced. Later, it gradually developed into a machine form, with modules or unit boards placed horizontally, and the probes collected data vertically. In order to improve efficiency, a single machine can be equipped with multiple probes. In the author, the maximum number of probes for a single machine is 16 and the acquisition is performed in units of boxes.
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