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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.

Currently,intelligent transportation systems(ITS) proposed a new demand that the VMS should have the ability to choose the most simple and effective means of communication according to the different environments as well as higher demands in the stability and reliability of the communication.In view of this situation,combined with the embedded technology and network communication technology,this paper proposed a communication system based on embedded highway VMS.The system uses MC703CDMA EV-DO 3G module and DM9000CIEP network chip,combined with the powerful networking capabilities of Linux operating system,has the ability of 3G wireless network,10/100M adaptive Ethernet communication and RS485 serial interface communication.The system has high effectiveness and stability in communication,at the same time it can selected different communication methods according to the specific environment.

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.

To obtain every single LED's contribution when they illuminate the target locations and to acquire,record or reappear some specific light patterns,this paper explores how to estimate the parameters of Pulse Width Modulation(PWM).These parameters are amplitude,frequency offset and phase delay,and they are generally used to control the LED points.Firstly,the frequency offset-phase delay space is dispersed into reticulated grid spaces,and a sparse model is established based on the measured data with sparsity characteristics in the grid space.Then,on the basis of the sparse model,very few samples are utilized to reconstruct the unknown parameters fast by means of Orthogonal Matching Pursuit(OMP) algorithm.Finally,an iterative refinement grid technique is introduced to optimize the sparse model so as to suppress the estimation error effectively.Experimental results indicate that the method presented in this paper can reconstruct the unknown parameters fast by using only 27.5% samples that of the traditional Nyquist sampling theorem.Simultaneously,this algorithm is found robustness when Signal to Noise Ratio(SNR) is higher than 20 db after lots of contrast tests in different noise conditions.

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.

The characteristics,basic structure and working principle of VFD display module is introduced.A design of hardware connection and software processes is given for the system,which is composed by the module with AT89C52 SCM.In this display program,the timing sequence of writing and reading is simulated by using general I/O port.Using specific implementation methods of C language,and rich display of LCD module,a better interface between SCM and VFD display module is realized,and has been applied to the actual workplace.Test result shows that the display system is stable,and has better display quality and faster refresh rate,it can achieve the objectives that use a host computer to control the VFD display module through serial ports.

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.

With the wide use of LED display,the era for perfect display-effect has arrived.However,different LED displays may differ in performance decided by many factors,including the characteristics of LED die,process,driver IC design,RD capability of manufacturer,etc.The phenomenon of color temperature deviation on white-field LED display was studied.The chromatograph differences of three primary colors in separate style and in white-field style were analyzed with chromatographic method,and the reason for the discrepancy was explored.