Search

LEDs have uniform problems include brightness aspect and color aspect,which would reduce the image quality of LED displays.This paper gives a method to correct the color gamut of LED displays.The method can solve the uniform problems,while correct the color gamut of LED displays accurately.This paper establishes a linear mathematical model of LED displays'colors,analyzing the target color gamut of LED displays.Then,the correction method with the target color gamut as LED displays'color gamut is introduced.Furthermore,white balance in color gamut correction method is introduced to fix the color coordinates of colors accurately.Experimental results showed that this method can correct the color gamut of LED displays into target color gamut accurately.

An efficient revising method was proposed to revise the display images of a Light Emission Diode(LED) captured by a color CCD camera.Firstly,the uniform standard white board was used to revise the vignetting phenomenon caused by a curved surface of color CCD camera in the manufacturing process.Then,on the basis of the distribution regularity of the lighting distribution curve of the LED,the deviation of LED itself caused by the camera position was revised also.The revising theory and revising process were described.Finally,relative data and conclusion were given.It shows that the uniform mean-square deviations of red,green and blue primaries have been decreased from 4.0% to 1.48%,3.1% to 1.36%,and 3.5% to 1.39%,respectively,after revising.It is shown that this method is an efficient one.It not only eliminates the vignetting phenomenon caused by the curved surface of the camera itself,but also removes the deviation caused by the capturing angle of the CCD camera.The experimental results meet the requirements of image revising basically.

A method by combination of a colorimeter and a color CCD to measure the brightness and chroma of color pixels of a Light Emitting Diode(LED) was proposed.Firstly,the color pixels of the LED were processed by the CCD camera and the brightness and chroma values of the LED pixels in RGB color space were calculated by image processing.Then,the multi-channel and adaptive matrix between RGB color space and CIE1931XYZ color space were established and the measured data of a few LED pixels were obtained by the colorimeter.With the RGB values and the measured data,the adaptive matrix could be calculated.Finally,the tristimulus values of the LEDs were calculated with the adaptive matrix.Experimental results indicate that the color difference between calculated data and measured data is less than 1 in an appropriate size of adaptive matrix,which can obtain the brightness and chroma of color pixels of the LED rapidly and precisely,and can correct the brightness and chroma of the LED screen.The method can be used to measure hundreds of thousands of LEDs accurately in a short time.

In order to segment each LED pixels from the image which is acquired by CCD and is used to brightness correction,a method based on optimal threshold segmentation with area constraint has been proposed.Based on optimal threshold method,taking prior information into account,an area constraint is introduced to restrain the range of threshold.Compared with traditional method,it is well done to avoid the LED region segmented connecting together.In the optimal threshold method with area constraint,the histogram of the captured image is generated,using the method of optimal threshold with area constraint,the optimal threshold is acquired.Finally,the optimal threshold method is used to segment the captured image.Experiments demonstrate that it is good to use this method to segment the LED pixels from the captured image,and also it can avoid the segmented region of LED pixels with a dense distribution connecting together.

A linear mathematical model is established to describe LED displays' colors accor-ding to LED's optical characters and the the pulse width modulation method of LED displays' control system.Furthermore,the mathematical model is connected with the visual perception in CIE1976LUV color space.This paper analyzed the relationship between visual perception and accuracy requirement of control system when the neighbouring gray levels and neighbouring colors of LEDs are discussed.Moreover,to calculate the control system's accuracy according to visual perception,the uniform problems of LED are discussed.This paper gives an algorithm to calculate the systemic accuracy of LED displays based on visual perception.With the algorithm,it is possible to design and optimize the LED displays' control system according to visual perception before the LED displays are produced.