| In general, linear array image sensor using one dimensional pixel array structure, by the relative motion of the image sensor and imaging objects to scan images. And it's image quality affected by image sensor, light intensity, speed matching and other factors. Time delay integration is that by using array image sensor to realize the function of the linear array scanning imaging, can realize multiple exposures on the same scene, equivalent to extend the exposure time, and effectively improve the Signal to Noise Ratio(SNR) and sensitivity of linear array image sensor. What's more, it will have good compatibility, the characteristics of high integration, low power consumption by using CMOS process, so the research of TDI CMOS image sensor image quality and imaging system research is of great significance.In order to improve the image quality of the TDI CMOS image sensor, the influence of integration time selected on image quality is studied. Based on the rolling shutter readout timing principle, the impacts of integration time on SNR and Modulation Transfer Function(MTF) are analyzed respectively. According to the results of the analysis, it is proposed that in the case of series selected, the optimal value exists in the selection of integration time, which makes a better image quality.To validate the conclusion, on the basis of self-developed TDI CMOS image sensor chip and FPGA development board, the imaging measurement system of TDI CMOS image sensor is set up. By using MTF×SNR as the image quality evaluating index in the experiment, the experimental results show that under the selected camera parameters, the stage is 8, and the light intensity is 20 lux, when the integration time is 64?s, the best image quality can be obtained and the MTF×SNR is maximum. In the design and application of TDI CMOS image sensor, the exposure time can be selected appropriately by according to the application requirements and combined with optimization method proposed in this paper. |
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