工业线阵CCD相机系统测试与噪声评估

为了快速评价工业线阵CCD相机质量,本文选择信噪比为评价因子,建立了测试系统,研究了基于相机输出图像测试相机噪声的方法。分析了线阵CCD相机的噪声,建立了一个基于固定模式和随机噪声的信噪比计算模型,并分析了相关双采样(CDS)过程对电源噪声的影响。设计了一套适于工业场所的相机快速信噪比测试系统,结合理论分析数据和实际测试图像数据,提出了仅通过输出的8bit图片计算各噪声参数的方案。最后,对测试系统引入的光源不均匀性噪声进行了讨论,并证明该实验平台光源符合工业标准EVM1288要求。实验结果表明:当相机模数(AD)转化设置为8.7dB时,输出信噪比可达44dB;若排除光源干扰,输出信噪比可达46dB。该方案简便快捷,满足工业现场对相机信噪比评估的要求。

Linear CCD camera System for industry measurement and its noise evaluation

To evaluate the imaging quality of a CCD camera rapidly, the Signal to Noise Ratio(SNR) was selected as the evaluation factors, a measurement system was constructed and methods to measure the camera's noise based on the output images of the camera were researched. The noise from the linear CCD camera was analyzed, a model for computing the SNR was established based on the fix pattern noise sources and temporal noise sources and the impact of Correlated Double Sample(CDS)processing on the power supply noise source was analyzed. A rapid measurement system for the SNR of camera in industry applications was designed, and a scheme to measure various noise sources was proposed by analyzing the theoretical model,practical tested data and 8 bit output images. Finally, the non-uniformity of the light source in the measurement system was discussed and it demonstrates that the light source meets the requirements of EVM1288 industry-standard. Experiment results indicate that the SNR of the camera reaches to 44 dB when the AD gain is set to be 8.7 dB, and it reaches to 46 dB if the interference of the non-uniformity from light source are eliminated. It concludes that the proposed scheme has higher measuring speeds, and satisfies the system requirements of SNR measurement for industry applications.