Modeling and simulation of subpixel imaging for area charge coupled device

In order to quantitatively investigate image quality improvement of area CCD subpixel imaging and influence of fill factor on image quality, a mathematical model was established to simulate subpixel imaging of array CCD with different fill factors. Without consideration of noise influence, simulation experiment for a sub-image of ISO12233 standard resolution card was performed on Matlab. Experiment results illustrate that, when fill factor is 100%, compared with common imaging mode of array CCD, gray mean gradient (GMG) of diagonal subpixel and four-point subpixel imaging mode was increased by 2.997 0, 3.413 6 respectively, and energy of Laplacian(EOL) is enhanced by 0.567 6, 0.747 8 respectively. With the same fill factor other than 100%, GMGs and EOLs of common imaging mode, diagonal subpixel imaging mode, and four-point subpixel mode are increasing in that order too. For four-point subpixel imaging mode, GMG of 69%, 44%, 25% fill factor is improved by 1.433 0, 3.337 3, 5.153 2 respectively compared with that of 100% fill factor, and EOL increased by 0.638 0, 1.704 4, 3.196 8 respectively. With the same imaging mode other than four-point subpixel, GMGs and EOLs of images obtained with CCDs whose fill factor is 100%, 69%, 44%, 25% increase too. Research shows that subpixel technique of array CCD can improve image quality, and four-point subpixel imaging mode provides more improvement on image quality than diagonal subpixel imaging mode. In the condition of signal-to-noise ratio is met, the image quality performance becomes better when fill factor decrease for the same CCD imaging mode.