Study Of Color Image Restoration Based On High Speed Large Array CMOS Digital Camera

With the rapid development of hardware manufacturers and IC technology,the digital imaging system based on CMOS grows quickly in recent years.Comparing to CCD sensor,CMOS has many advantages,such as simple structure and driving,high degree of integration,low power consumption,flexible control,short development cycle and high radiation tolerance.CMOS sensor can output digital signal directly,so it plays a more important part in high speed digital imaging field.CMOS digital imaging system has been used in space exploration,such as aviation optical remote sensing and star sensor,and accomplished many achievements already.High speed large array digital imaging technology has been widely used in domestic space remote sensing,medical,traffic monitor,smartphone,automobile reversing radar and other fields.High degree of integration and low cost high speed large array color imaging system has been applied to many fields and become an indispensable part.In order to reduce cost and size in traditional three sensors color imaging system,a solution is proposed by an engineer of Kodak: coating a Mosaic membrane on the sensor element surface.In this Mosaic membrane,red,green and blue are placed in special on a definite principle.After coating Mosaic membrane,digital imaging system only can output bayer template image.So we can choose appropriate color image interpolation algorithm to restore color image from bayer template image.This dissertation introduced several traditional color image interpolation algorithms,and understood the advantages and disadvantages of these algorithms.Taking a series of test images for instance,we use peak signal-to-noise ratio to evaluate these algorithms.Combining with the features of these algorithms,this paper proposed a new color image interpolation algorithm based on bayer template.Comparing to classic bilinear interpolation algorithm,PSNR has been increased 7.2%.This dissertation designed a color image restoration system.CMOS is driven by FPGA to implement difference level transformation,combining with color image restoration module and picture transfer protocol Camlink in this system.The proposed algorithm in this dissertation has been applied in color image restoration system by VHDL.The size of this system is 16.2cm×15.4cm×11.5cm,the weight is 1.5kg,image resolution is 5120×3840,frame frequency is 30 Hz.The 16 data channels are used to transfer 12-bit data words from sensor to receiver,using internal PLL produce high speed difference synchronous clock to implement LVDS electric level conversion,and then the image data is transferred and displayed by Cam Link protocol.