In recent years, full color indoor LED display screen in the stadium, road traffic, advertising, leasing and other aspects of the application of a rapid growth trend. From the current market demand analysis, the necessity of on-site proofreading is more and more prominent.
Uniform proofreading can be classified as: factory proofreading, repair proofreading, service area proofreading and on-site proofreading.
Generally speaking, when the full color LED display screen is running to a certain time, all LED leds will have a luminance attenuation, and the attenuation curve of the tri-primary color tube is not common. Therefore, their brightness will also be compared with the factory brightness has decreased. However, the difference in the photoelectric characteristics of each LED makes the degree of decrease in their brightness cause errors. Therefore, when the display screen is used for a certain period of time, the luminance of the luminescent tube will decrease to different degrees, making the display uneven between pixels. Then, compared with the screen when the factory starts, the whole picture will be displayed in a granular state, or the overall luminance will decrease. Three - color tube attenuation curve does not make white balance, color temperature and other changes.
In practice, due to the attenuation of LED leds and the change of other factors such as ambient temperature, it is almost impossible to avoid the deterioration of the function of the excellent display screen at the factory. It is not feasible to take apart the installed LED display screen and send it back to the factory for proofreading. Given these features, it is necessary for display manufacturers to check on site to ensure that the display remains as it was when it was shipped out of the factory throughout the display's life cycle. Several on-site proofreading methods:
I. calibration method based on the running time of LED: this is an early on-site calibration method, which is to conduct on-site calibration of the display screen based on shadowing and recording the running time of each LED module. By roughly calculating the working time of each LED, measuring their respective uniform brightness attenuation, estimating different proofreading levels, and then sending to each LED module for corresponding adjustment. This approach does not require any human input. However, this approach ignores an important problem, that the estimated LED attenuation frequency from the running time is not suitable for each LED. With the increase of running time, the fluctuation scale of LED attenuation frequency becomes larger and larger. The calibration conducted on a uniform basis makes some leds close to the calibration level, but makes other leds more contrary. Because the brightness level between each module is not the same, there is no effective way to adjust the brightness of these modules do not match, therefore, in the running time between different modules for uniformity adjustment, will occur a series of problems, and crucially, this method can not complete the calibration between pixels. Therefore, through this kind of proofreading in the future, the display screen gives a person the whole feeling to appear Mosaic phenomenon, can not improve the uniformity of the display screen in the later stage.
Second, according to the scene of the common proofreading way: in order to thoroughly improve uniformity of the display screen problem, need to use special equipment to collect in the field of LED display screen light color information of each pixel for rapid collection, through the practice of the related algorithms for each LED luminous tube compensate the attenuation degree, and then complete the real in the sense of mutual check, even about running not engraved with the LED module to complete the calibration of pixel level. Through proofreading, the full color led display screen can be restored to the uniform display function of the factory.